MIT News - Physicshttp://news.mit.edu/topic/mitphysics-rss.xml
MIT News is dedicated to communicating to the media and the public the news and achievements of the students, faculty, staff and the greater MIT community.enSun, 18 Mar 2018 23:59:59 -0400Scientists detect radio echoes of a black hole feeding on a starhttp://news.mit.edu/2018/scientists-detect-radio-echoes-black-hole-feeding-star-0319
Signals suggest black hole emits a jet of energy proportional to the stellar material it gobbles up.Sun, 18 Mar 2018 23:59:59 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2018/scientists-detect-radio-echoes-black-hole-feeding-star-0319<p>On Nov. 11, 2014, a global network of telescopes picked up signals from 300 million light years away that were created by a tidal disruption flare — an explosion of electromagnetic energy that occurs when a black hole rips apart a passing star. Since this discovery, astronomers have trained other telescopes on this very rare event to learn more about how black holes devour matter and regulate the growth of galaxies.</p>
<p>Scientists from MIT and Johns Hopkins University have now detected radio signals from the event that match very closely with X-ray emissions produced from the same flare 13 days earlier. They believe these radio “echoes,” which are more than 90 percent similar to the event’s X-ray emissions, are more than a passing coincidence. Instead, they appear to be evidence of a giant jet of highly energetic particles streaming out from the black hole as stellar material is falling in.</p>
<p>Dheeraj Pasham, a postdoc in MIT’s Kavli Institute for Astrophysics and Space Research, says the highly similar patterns suggest that the power of the jet shooting out from the black hole is somehow controlled by the rate at which the black hole is feeding on the obliterated star.</p>
<p>“This is telling us the black hole feeding rate is controlling the strength of the jet it produces,” Pasham says. “A well-fed black hole produces a strong jet, while a malnourished black hole produces a weak jet or no jet at all. This is the first time we’ve seen a jet that’s controlled by a feeding supermassive black hole.”</p>
<p>Pasham says scientists have suspected that black hole jets are powered by their accretion rate, but they have never been able to observe this relationship from a single event.</p>
<p>“You can do this only with these special events where the black hole is just sitting there doing nothing, and then suddenly along comes a star, giving it a lot of fuel to power itself,” Pasham says. “That’s the perfect opportunity to study such things from scratch, essentially.”</p>
<p>Pasham and his collaborator, Sjoert van Velzen of Johns Hopkins University, report their results in a paper published this week in the <em>Astrophysical Journal.</em></p>
<p><strong>Up for debate</strong></p>
<p>Based on theoretical models of black hole evolution, combined with observations of distant galaxies, scientists have a general understanding for what transpires during a tidal disruption event: As a star passes close to a black hole, the black hole’s gravitational pull generates tidal forces on the star, similar to the way in which the moon stirs up tides on Earth.</p>
<p>However, a black hole’s gravitational forces are so immense that they can disrupt the star, stretching and flattening it like a pancake and eventually shredding the star to pieces. In the aftermath, a shower of stellar debris rains down and gets caught up in an accretion disk — a swirl of cosmic material that eventually funnels into and feeds the black hole.</p>
<p>This entire process generates colossal bursts of energy across the electromagnetic spectrum. Scientists have observed these bursts in the optical, ultraviolet, and X-ray bands, and also occasionally in the radio end of the spectrum. The source of the X-ray emissions is thought to be ultrahot material in the innermost regions of the accretion disk, which is just about to fall into the black hole. Optical and ultraviolet emissions likely arise from material further out in the disk, which will eventually be pulled into the black hole.</p>
<p>However, what gives rise to radio emissions during a tidal disruption flare has been up for debate.</p>
<p>“We know that the radio waves are coming from really energetic electrons that are moving in a magnetic field — that is a well-established process,” Pasham says. “The debate has been, where are these really energetic electrons coming from?”</p>
<p>Some scientists propose that, in the moments after the stellar explosion, a shockwave propagates outward and energizes the plasma particles in the surrounding medium, in a process that in turn emits radio waves. In such a scenario, the pattern of emitted radio waves would look radically different from the pattern of X-rays produced from infalling stellar debris.</p>
<p>“What we found basically challenges this paradigm,” Pasham says.</p>
<p><strong>A shifting pattern</strong></p>
<p>Pasham and van Velzen looked through data recorded from a tidal disruption flare discovered in 2014 by the global telescope network ASASSN (All-sky Automated Survey for Supernovae). Soon after the initial discovery, multiple electromagnetic telescopes focused on the event, which astronomers coined ASASSN-14li. Pasham and van Velzen perused radio data from three telescopes of the event over 180 days.</p>
<p>The researchers looked through the compiled radio data and discovered a clear resemblance to patterns they had previously observed in X-ray data from the same event. When they fit the radio data over the X-ray data, and shifted the two around to compare their similarities, they found the datasets were most similar, with a 90 percent resemblance, when shifted by 13 days. That is, the same fluctuations in the X-ray spectrum appeared 13 days later in the radio band.</p>
<p>“The only way that coupling can happen is if there is a physical process that is somehow connecting the X-ray-producing accretion flow with the radio-producing region,” Pasham says.</p>
<p>From this same data, Pasham and van Velzen calculated the size of the X-ray-emitting region to be about 25 times the size of the sun, while the radio-emitting region was about 400,000 times the solar radius.</p>
<p>“It’s not a coincidence that this is happening,” Pasham says. “Clearly there’s a causal connection between this small region producing X-rays, and this big region producing radio waves.”</p>
<p>The team proposes that the radio waves were produced by a jet of high-energy particles that began to stream out from the black hole shortly after the black hole began absorbing material from the exploded star. Because the region of the jet where these radio waves first formed was incredibly dense (tightly packed with electrons), a majority of the radio waves were immediately absorbed by other electrons.</p>
<p>It was only when electrons traveled downstream of the jet&nbsp;that the radio waves could escape — producing the signal that the researchers eventually detected. Thus, they say, the strength of the jet must be controlled by the accretion rate, or the speed at which the black hole is consuming X-ray-emitting stellar debris.</p>
<p>Ultimately, the results may help scientists better characterize the physics of jet behavior — an essential ingredient in modeling the evolution of galaxies. It’s thought that galaxies grow by producing new stars, a process that requires very cold temperatures. When a black hole emits a jet of particles, it essentially heats up the surrounding galaxy, putting a temporary stop on stellar production. Pasham says the team’s new insights into jet production and black hole accretion may help to simplify models of galaxy evolution.</p>
<p>“If the rate at which the black hole is feeding is proportional to the rate at which it’s pumping out energy, and if that really works for every black hole, it’s a simple prescription you can use in simulations of galaxy evolution,” Pasham says. “So this is hinting toward some bigger picture.”</p>
Artist's impression of an inner accretion flow and a jet from a supermassive black hole when it is actively feeding, for example, from a star that it recent tore apart.Image: ESO/L. CalçadaAstronomy, Astrophysics, Black holes, Kavli Institute, Physics, Research, School of Science, Space, astronomy and planetary science3Q: Zach Hartwig on MIT&#039;s big push on fusionhttp://news.mit.edu/2018/3q-zach-hartwig-mit-big-push-fusion-0309
Researchers will work with industrial collaborators to pursue fusion as a source of carbon-free power.Fri, 09 Mar 2018 00:00:00 -0500MIT News Officehttp://news.mit.edu/2018/3q-zach-hartwig-mit-big-push-fusion-0309<p><em>Today, MIT <a href="http://news.mit.edu/2018/mit-newly-formed-company-launch-novel-approach-fusion-power-0309">announced plans</a> to work with a newly formed company, Commonwealth Fusion Systems (CFS), to realize the promise of fusion as a source of unlimited, safe, carbon-free energy. Zach Hartwig, an assistant professor of nuclear science and engineering, is one of the Institute’s leads on the effort, along with others in MIT’s Plasma Fusion and Science Center (PSFC). He spoke with </em>MIT News<em> about the group’s vision for a fusion-powered future.</em></p>
<p><strong>Q: </strong>Why is this new collaboration needed to support fusion energy?</p>
<p><strong>A:</strong> Mitigating global climate change requires new sources of zero-carbon energy as soon as we can deliver them, and we are going to need a completely new approach to ensure that fusion energy can be a significant part of the solution.</p>
<p>The hard reality of climate change is that every single nation that has ever industrialized and made a better life for its citizens did so at the expense of the climate. There is, at present, simply no other way to do this than to dump carbon dioxide into the atmosphere by burning fossil fuels for energy.</p>
<p>As a global society, we have to do better. Fusion energy represents one tremendously attractive pathway, if we can demonstrate its potential and accelerate its commercial deployment. This is going to require new models of innovation that couple research institutions, such as MIT, with private companies, such as CFS, that are capable of commercializing fusion — and then providing that relationship with sustainable, patient capital that can fund the development of breakthrough energy solutions at scale.</p>
<p>Fusion is the fundamental energy source of the universe, powering our sun and the distant stars. The promise of harnessing fusion to produce energy on Earth is simple: limitless, safe, zero-carbon energy.</p>
<p>Like the governments of many nations, the U.S. has funded basic research on fusion science and technology since the 1950s, making tremendous progress toward the goal of fusion energy. MIT has long been a leading institution in fusion research, receiving research support primarily from the Department of Energy, including the funding of three major fusion energy experiments at MIT culminating in the Alcator C-Mod tokamak, which ended 25 years of operation in 2016. The DOE continues its support of fusion energy research at other facilities around the U.S. and the world, including the ITER experiment now under construction in France.</p>
<p>However, the mission and structure of federal research sponsorship does not extend to commercialization of the basic research it funds; this is the role of private companies, which are structured to raise capital and efficiently deploy competitive technologies into the commercial marketplace. But this raises a crucial question: How does promising, federally funded research transition into a robust commercial product — particularly in fusion energy, where the timelines and financial costs are higher than in many other technologies?</p>
<p>We believe that this new model of collaboration between MIT and CFS provides this bridge. MIT continues its involvement beyond the federally funded research stage, providing scientific expertise and infrastructure for research, while CFS provides stable funding from long-term investment and a mechanism to accelerate and commercialize the technology.</p>
<p>Importantly, this model is not limited to fusion energy, but creates a new framework for research universities and energy companies to partner on large-scale, long-term energy projects.</p>
<p>A critical, relatively recent technology breakthrough plays an important enabling role in this collaboration: a class of materials known as high-temperature superconductors that have only become commercially available with sufficient performance and quantity for fusion application within the last five years or so.</p>
<p>These materials will enable MIT and CFS to substantially increase the performance of superconducting fusion magnets, the principal initial focus of the research collaboration. These magnets will lead to dramatically smaller, lower-cost fusion devices that can produce net energy up to several hundred megawatts of power, and, most importantly, be strongly competitive in the energy marketplace in less than 20 years.</p>
<p><strong>Q: </strong>What is Commonwealth Fusion Systems? Is it related to MIT?</p>
<p><strong>A:</strong> Commonwealth Fusion Systems (CFS) is an independent, for-profit company created by former MIT staff and students to help accelerate the commercialization of fusion energy. CFS will sponsor research at MIT and work closely with us to determine and execute the research program leading to an experiment we call SPARC. We anticipate that this relationship will be an ongoing and long-term one.</p>
<p>CFS has raised significant funding to support efforts at MIT to achieve fusion energy and to conduct related business activities. The first part of these <a href="http://news.mit.edu/2018/new-era-fusion-research-mit-eni-0309">investments come from Eni</a>, a multinational energy company seeking to diversify its portfolio with a forward-looking investment in fusion energy.</p>
<p>Some of this funding will come to PSFC and others at MIT, to support our research; some of it will go to support CFS’s own R&amp;D; and some may go to other institutions with relevant expertise. As with other sponsored research on campus, the results of MIT’s research will be publishable, and the Institute will own and license the intellectual property rights to discoveries made by its scientists along the way. The funding will also support MIT’s educational mission, providing research opportunities for graduate students.</p>
<p><strong>Q: </strong>How does this effort differ from other ongoing approaches to fusion energy?</p>
<p><strong>A: </strong>Fusion energy is widely recognized as having enormous potential. It is, therefore, pursued by a variety of players in a variety of ways.</p>
<p>One can broadly classify these efforts into two categories: government-funded research in magnetic confinement fusion, focusing primarily on the tokamak concept with the international ITER project as its focal point; and privately funded companies pursuing primarily non-tokamak-based devices. These two approaches are different from each other in their funding sources, organizational structures, mission objectives, and risk management philosophies.</p>
<p>The government-funded tokamak approach to fusion via ITER is a massive long-term effort supported by the governments of six nations — China, India, Japan, Russia, South Korea, and the United States — and the European Union. Being built in the south of France, ITER is a fusion science experiment designed to produce net fusion power sometime after 2035, if the present schedule holds.</p>
<p>ITER leverages proven physics built on 50 years of successful government-backed research, mitigating a critical risk in the underlying science. On the other hand, its sheer scale requires very high costs, international organizational challenges and, ultimately, long timelines that put fusion power on the grid sometime after 2060, quite possibly too late to substantially mitigate global warming associated with combustion of fossil fuels.</p>
<p>In contrast, the private fusion companies are smaller, nimbler, and learn by iterating quickly. This approach, coupled with private funding, provides driving pressure to move as quickly and efficiently as possible to commercialize fusion. Their universal challenge, however, is that their fusion concepts are based on unproven physics that, at best, may require a long time and extensive resources to prove the science and, at worst, may be unable to scale to the performance required for a fusion power plant.</p>
<p>The high-field pathway to fusion energy proposed by MIT and CFS seeks to take the best of both approaches — coupling the proven physics of the tokamak with the drive of a company focused on commercialization — and isolating the majority of the technical risk in the engineering development of the high-field magnets.</p>
<p>Overall, we believe two things about all of the ongoing efforts on fusion energy, both government- and privately funded. First, fusion energy is too important to solving major challenges facing humanity to focus exclusively on a single approach, particularly where parallel technology and funding pathways can exist side by side: There’s value in carefully incorporating a diversity of approaches to fusion energy in order to benefit from the different risk and reward trade-offs embodied in each. Second, all of the approaches are part of a nascent but growing fusion ecosystem that can work together in a surprising number of areas to achieve our mutual goal of fusion energy in time to make a difference.</p>
Zach HartwigPhoto: Bryce VickmarkFusion, Nuclear science and engineering, School of Engineering, Plasma Science and Fusion Center, Alternative energy, Renewable energy, Energy, 3 Questions, Industry, Physics, Nuclear power and reactorsMIT and newly formed company launch novel approach to fusion powerhttp://news.mit.edu/2018/mit-newly-formed-company-launch-novel-approach-fusion-power-0309
Goal is for research to produce a working pilot plant within 15 years.Fri, 09 Mar 2018 00:00:00 -0500David Chandler | MIT News Officehttp://news.mit.edu/2018/mit-newly-formed-company-launch-novel-approach-fusion-power-0309<p>Progress toward the long-sought dream of fusion power — potentially an inexhaustible and zero-carbon source of energy — could be about to take a dramatic leap forward.</p>
<p>Development of this carbon-free, combustion-free source of energy is now on a faster track toward realization, thanks to a <a href="http://news.mit.edu/2018/3q-zach-hartwig-mit-big-push-fusion-0309">collaboration between MIT and a new private company</a>, Commonwealth Fusion Systems. CFS will join with MIT to carry out rapid, staged research leading to a new generation of fusion experiments and power plants based on advances in high-temperature superconductors — work made possible by decades of federal government funding for basic research.</p>
<p>CFS is announcing today that it has attracted an investment of $50 million in support of this effort from the Italian energy company Eni. In addition, CFS continues to seek the support of additional investors. CFS will fund fusion research at MIT as part of this collaboration, with an ultimate goal of rapidly commercializing fusion energy and establishing a new industry.</p>
<p>“This is an important historical moment: Advances in superconducting magnets have put fusion energy potentially within reach, offering the prospect of a safe, carbon-free energy future,” says MIT President L. Rafael Reif. “As humanity confronts the rising risks of climate disruption, I am thrilled that MIT is joining with industrial allies, both longstanding and new, to run full-speed toward this transformative vision for our shared future on Earth.”</p>
<p>“Everyone agrees on the eventual impact and the commercial potential of fusion power, but then the question is: How do you get there?” adds Commonwealth Fusion Systems CEO Robert Mumgaard SM ’15, PhD ’15. “We get there by leveraging the science that’s already developed, collaborating with the right partners, and tackling the problems step by step.”</p>
<p>MIT Vice President for Research Maria Zuber, who has written <a href="https://www.bostonglobe.com/opinion/2018/03/09/new-approach-fusion-energy-starts-today/cc7kpF93xLaopO5xdobKIO/story.html">an op-ed on the importance of this news</a> that appears in today’s <em>Boston Globe</em>, notes that MIT’s collaboration with CFS required concerted effort among people and offices at MIT that support innovation:&nbsp;“We are grateful for the MIT team that worked tirelessly to form this collaboration. Associate Provost Karen Gleason’s leadership was instrumental — as was the creativity, diligence, and care of the Office of the General Counsel, the Office of Sponsored Programs, the Technology Licensing Office, and the MIT Energy Initiative. A great job by all.”</p>
<p><strong>Superconducting magnets are key</strong></p>
<p>Fusion, the process that powers the sun and stars, involves light elements, such as hydrogen, smashing together to form heavier elements, such as helium — releasing prodigious amounts of energy in the process. This process produces net energy only at extreme temperatures of hundreds of millions of degrees Celsius, too hot for any solid material to withstand. To get around that, fusion researchers use magnetic fields to hold in place the hot plasma — a kind of gaseous soup of subatomic particles — keeping it from coming into contact with any part of the donut-shaped chamber.</p>
<p>The new effort aims to build a compact device capable of generating 100 million watts, or 100 megawatts (MW), of fusion power. This device will, if all goes according to plan, demonstrate key technical milestones needed to ultimately achieve a full-scale prototype of a fusion power plant that could set the world on a path to low-carbon energy. If widely disseminated, such fusion power plants could meet a substantial fraction of the world’s growing energy needs while drastically curbing the greenhouse gas emissions that are causing global climate change.</p>
<p>“Today is a very important day for us,” says Eni CEO Claudio Descalzi. “Thanks to this agreement, Eni takes a significant step forward toward the development of alternative energy sources with an ever-lower environmental impact. Fusion is the true energy source of the future, as it is completely sustainable, does not release emissions or long-term waste, and is potentially inexhaustible. It is a goal that we are increasingly determined to reach quickly.”</p>
<p>CFS will support more than $30 million of MIT research over the next three years through investments by Eni and others. This work will aim to develop the world’s most powerful large-bore superconducting electromagnets — the key component that will enable construction of a much more compact version of a fusion device called a tokamak. The magnets, based on a superconducting material that has only recently become available commercially, will produce a magnetic field four times as strong as that employed in any existing fusion experiment, enabling a more than tenfold increase in the power produced by a tokamak of a given size.</p>
<p><strong>Conceived at PSFC</strong></p>
<p>The project was conceived by researchers from MIT’s Plasma Science and Fusion Center, led by PSFC Director Dennis Whyte, Deputy Director Martin Greenwald, and a team that grew to include representatives from across MIT, involving disciplines from engineering to physics to architecture to economics. The core PSFC team included Mumgaard, Dan Brunner PhD ’13, and Brandon Sorbom PhD ’17 —&nbsp;all now leading CFS — as well as Zach Hartwig PhD ’14, now an assistant professor of nuclear science and engineering at MIT.</p>
<p>Once the superconducting electromagnets are developed by researchers at MIT and CFS — expected to occur within three years — MIT and CFS will design and build a compact and powerful fusion experiment, called SPARC, using those magnets. The experiment will be used for what is expected to be a final round of research enabling design of the world’s first commercial power-producing fusion plants.</p>
<p>SPARC is designed to produce about 100 MW of heat. While it will not turn that heat into electricity, it will produce, in pulses of about 10 seconds, as much power as is used by a small city. That output would be more than twice the power used to heat the plasma, achieving the ultimate technical milestone: positive net energy from fusion.</p>
<p>This demonstration would establish that a new power plant of about twice SPARC’s diameter, capable of producing commercially viable net power output, could go ahead toward final design and construction. Such a plant would become the world’s first true fusion power plant, with a capacity of 200 MW of electricity, comparable to that of most modern commercial electric power plants. At that point, its implementation could proceed rapidly and with little risk, and such power plants could be demonstrated within 15 years, say Whyte, Greenwald, and Hartwig.</p>
<p><strong>Complementary to ITER</strong></p>
<p>The project is expected to complement the research planned for a large international collaboration called ITER, currently under construction as the world’s largest fusion experiment at a site in southern France. If successful, ITER is expected to begin producing fusion energy around 2035.</p>
<p>“Fusion is way too important for only one track,” says Greenwald, who is a senior research scientist at PSFC.</p>
<p>By using magnets made from the newly available superconducting material — a steel tape coated with a compound called yttrium-barium-copper oxide (YBCO) — SPARC is designed to produce a fusion power output about a fifth that of ITER, but in a device that is only about 1/65 the volume, Hartwig says. The ultimate benefit of the YBCO tape, he adds, is that it drastically reduces the cost, timeline, and organizational complexity required to build net fusion energy devices, enabling new players and new approaches to fusion energy at university and private company scale. &nbsp;</p>
<p>The way these high-field magnets slash the size of plants needed to achieve a given level of power has repercussions that reverberate through every aspect of the design. Components that would otherwise be so large that they would have to be manufactured on-site could instead be factory-built and trucked in; ancillary systems for cooling and other functions would all be scaled back proportionately; and the total cost and time for design and construction would be drastically reduced.</p>
<p>“What you’re looking for is power production technologies that are going to play nicely within the mix that’s going to be integrated on the grid in 10 to 20 years,” Hartwig says. “The grid right now is moving away from these two- or three-gigawatt monolithic coal or fission power plants. The range of a large fraction of power production facilities in the U.S. is now is in the 100 to 500 megawatt range. Your technology has to be amenable with what sells to compete robustly in a brutal marketplace.”</p>
<p>Because the magnets are the key technology for the new fusion reactor, and because their development carries the greatest uncertainties, Whyte explains, work on the magnets will be the initial three-year phase of the project — building upon the strong foundation of federally funded research conducted at MIT and elsewhere. Once the magnet technology is proven, the next step of designing the SPARC tokamak is based on a relatively straightforward evolution from existing tokamak experiments, he says.</p>
<p>“By putting the magnet development up front,” says Whyte, the Hitachi America Professor of Engineering and head of MIT’s Department of Nuclear Science and Engineering, “we think that this gives you a really solid answer in three years, and gives you a great amount of confidence moving forward that you’re giving yourself the best possible chance of answering the key question, which is: Can you make net energy from a magnetically confined plasma?”</p>
<p>The research project aims to leverage the scientific knowledge and expertise built up over decades of government-funded research — including MIT’s work, from 1971 to 2016, with its Alcator C-Mod experiment, as well as its predecessors — in combination with the intensity of a well-funded startup company. Whyte, Greenwald, and Hartwig say that this approach could greatly shorten the time to bring fusion technology to the marketplace — while there’s still time for fusion to make a real difference in climate change.</p>
<p><strong>MITEI participation</strong></p>
<p>Commonwealth Fusion Systems is a private company and will join the <a href="http://energy.mit.edu/">MIT Energy Initiative</a> (MITEI) as part of a new university-industry partnership built to carry out this plan. The collaboration between MITEI and CFS is expected to bolster MIT research and teaching on the science of fusion, while at the same time building a strong industrial partner that ultimately could be positioned to bring fusion power to real-world use.</p>
<p>“MITEI has created a new membership specifically for energy startups, and CFS is the first company to become a member through this new program,” says MITEI Director Robert Armstrong, the Chevron Professor of Chemical Engineering at MIT. “In addition to providing access to the significant resources and capabilities of the Institute, the membership is designed to expose startups to incumbent energy companies and their vast knowledge of the energy system. It was through their engagement with MITEI that Eni, one of MITEI’s founding members, became aware of SPARC’s tremendous potential for revolutionizing the energy system.”</p>
<p>Energy startups often require significant research funding to further their technology to the point where new clean energy solutions can be brought to market. Traditional forms of early-stage funding are often incompatible with the long lead times and capital intensity that are well-known to energy investors.</p>
<p>“Because of the nature of the conditions required to produce fusion reactions, you have to start at scale,” Greenwald says. “That’s why this kind of academic-industry collaboration was essential to enable the technology to move forward quickly. This is not like three engineers building a new app in a garage.”</p>
<p>Most of the initial round of funding from CFS will support collaborative research and development at MIT to demonstrate the new superconducting magnets.&nbsp; The team is confident that the magnets can be successfully developed to meet the needs of the task. Still, Greenwald adds, “that doesn’t mean it’s a trivial task,” and it will require substantial work by a large team of researchers. But, he points out, others have built magnets using this material, for other purposes, which had twice the magnetic field strength that will be required for this reactor. Though these high-field magnets were small, they do validate the basic feasibility of the concept.</p>
<p>In addition to its support of CFS, Eni has <a href="http://news.mit.edu/2018/new-era-fusion-research-mit-eni-0309">also announced an agreement</a> with MITEI to fund fusion research projects run out of PSFC’s Laboratory for Innovation in Fusion Technologies. The expected investment in these research projects amounts to about $2 million in the coming years.</p>
<p><strong>“Conservative physics”</strong></p>
<p>SPARC is an evolution of a tokamak design that has been studied and refined for decades. This included work at MIT that began in the 1970s, led by professors Bruno Coppi and Ron Parker, who developed the kind of high-magnetic-field fusion experiments that have been operated at MIT ever since, setting numerous fusion records.</p>
<p>“Our strategy is to use conservative physics, based on decades of work at MIT and elsewhere,” Greenwald says. “If SPARC does achieve its expected performance, my sense is that’s sort of a Kitty Hawk moment for fusion, by robustly demonstrating net power, in a device that scales to a real power plant.”</p>
Visualization of the proposed SPARC tokamak experiment. Using high-field magnets built with newly available high-temperature superconductors, this experiment would be the first controlled fusion plasma to produce net energy output.
Visualization by Ken Filar, PSFC research affiliateFusion, Nuclear science and engineering, School of Engineering, Plasma Science and Fusion Center, Alternative energy, Renewable energy, Energy, Industry, Nuclear power and reactors, PhysicsA new era in fusion research at MIThttp://news.mit.edu/2018/new-era-fusion-research-mit-eni-0309
MIT Energy Initiative founding member Eni announces support for key research through MIT Laboratory for Innovation in Fusion Technologies.Fri, 09 Mar 2018 00:00:00 -0500Francesca McCaffrey | MIT Energy Initiativehttp://news.mit.edu/2018/new-era-fusion-research-mit-eni-0309<p>A new chapter is beginning for fusion energy research at MIT.</p>
<p>This week the Italian energy company Eni, a founding member of the MIT Energy Initiative (MITEI), announced it has reached an agreement with MIT to fund fusion research projects run out of the MIT Plasma Science and Fusion Center (PSFC)’s newly created Laboratory for Innovation in Fusion Technologies (LIFT). The expected investment in these research projects will amount to about $2 million over the following years.</p>
<p>This is part of a <a href="http://news.mit.edu/2018/mit-newly-formed-company-launch-novel-approach-fusion-power-0309">broader engagement </a>with fusion research and the Institute as a whole: Eni also announced a commitment of $50 million to a new private company with roots at MIT, Commonwealth Fusion Systems (CFS), which aims to make affordable, scalable <a href="http://news.mit.edu/2018/3q-zach-hartwig-mit-big-push-fusion-0309">fusion power a reality</a>.</p>
<p>“This support of LIFT is a continuation of Eni’s commitment to meeting growing global energy demand while tackling the challenge of climate change through its research portfolio at MIT,” says Robert C. Armstrong, MITEI’s director and the Chevron Professor of Chemical Engineering at MIT. “Fusion is unique in that it is a zero-carbon, dispatchable, baseload technology, with a limitless supply of fuel, no risk of runaway reaction, and no generation of long-term waste. It also produces thermal energy, so it can be used for heat as well as power.”</p>
<p>Still, there is much more to do along the way to perfecting the design and economics of compact fusion power plants. Eni will fund research projects at LIFT that are a continuation of this research and focus on fusion-specific solutions. “We are thrilled at PSFC to have these projects funded by Eni, who has made a clear commitment to developing fusion energy,” says Dennis Whyte, the director of PSFC and the Hitachi America Professor of Engineering at MIT. “LIFT will focus on cutting-edge technology advancements for fusion, and will significantly engage our MIT students who are so adept at innovation.”</p>
<p><strong>Tackling fusion’s challenges</strong></p>
<p>The inside of a fusion device is an extreme environment. The creation of fusion energy requires the smashing together of light elements, such as hydrogen, to form heavier elements such as helium, a process that releases immense amounts of energy. The temperature at which this process takes place is too hot for solid materials, necessitating the use of magnets to hold the hot plasma in place.</p>
<p>One of the projects PSFC and Eni intend to carry out will study the effects of high magnetic fields on molten salt fluid dynamics. One of the key elements of the fusion pilot plant currently being studied at LIFT is the liquid immersion blanket, essentially a flowing pool of molten salt that completely surrounds the fusion energy core. The purpose of this blanket is threefold: to convert the kinetic energy of fusion neutrons to heat for eventual electricity production; to produce tritium — a main component of the fusion fuel; and to prevent the neutrons from reaching other parts of the machine and causing material damage.</p>
<p>It’s critical for researchers to be able to predict how the molten salt in such an immersion blanket would move when subjected to high magnetic fields such as those found within a fusion plant. As such, the researchers and their respective teams plan to study the effects of these magnetohydrodynamic forces on the salt’s fluid dynamics.</p>
<p><strong>A history of innovation</strong></p>
<p>During the 23 years MIT’s Alcator C-Mod tokamak fusion experiment was in operation, it repeatedly advanced records for plasma pressure in a magnetic confinement device. Its compact, high-magnetic-field fusion design confined superheated plasma in a small donut-shaped chamber.</p>
<p>“The key to this success was the innovations pursued more than 20 years ago at PSFC in developing copper magnets that could access fields well in excess of other fusion experiments. The coupling between innovative technology development and advancing fusion science is in the DNA of the Plasma Science and Fusion Center,” says PSFC Deputy Director Martin Greenwald.</p>
<p>In its final run in 2016, Alcator C-Mod set a new world record for plasma pressure, the key ingredient to producing net energy from fusion. Since then, PSFC researchers have used data from these decades of C-Mod experiments to continue to advance fusion research. Just last year, they used C-Mod data to create a new method of heating fusion plasmas in tokamaks which could result in the heating of ions to energies an order of magnitude greater than previously reached.</p>
<p><strong>A commitment to low-carbon energy</strong></p>
<p>MITEI’s mission is to advance low-carbon and no-carbon emissions solutions to efficiently meet growing global energy needs. Critical to this mission are collaborations between academia, industry, and government — connections MITEI helps to develop in its role as MIT’s hub for multidisciplinary energy research, education, and outreach.</p>
<p>Eni is an inaugural, founding member of the MIT Energy Initiative, and it was through their engagement with MITEI that they became aware of the fusion technology commercialization being pursued by CFS and its immense potential for revolutionizing the energy system. It was through these discussions, as well, that Eni investors learned of the high-potential fusion research projects taking place through LIFT at MIT, spurring them to support the future of fusion at the Institute itself.</p>
<p>Eni CEO Claudio Descalzi said, “Today is a very important day for us. Thanks to this agreement, Eni takes a significant step forward toward the development of alternative energy sources with an ever lower environmental impact. Fusion is the true energy source of the future, as it is completely sustainable, does not release emissions or waste, and is potentially inexhaustible. It is a goal that we are determined to reach quickly.”<em>&nbsp;</em>He added, “We are pleased and excited to pursue such a challenging goal with a collaborator like MIT, with unparalleled experience in the field and a long-standing and fruitful alliance with Eni.”</p>
<p>These fusion projects are the latest in a line of MIT-Eni collaborations on low- and no-carbon energy projects. One of the earliest of these was the Eni-MIT Solar Frontiers Center, established in 2010 at MIT. Through its mission to develop competitive solar technologies, the center’s research has yielded the thinnest, lightest solar cells ever produced, effectively able to turn any surface, from fabric to paper, into a functioning solar cell. The researchers at the center have also developed new, luminescent materials that could allow windows to efficiently collect solar power.</p>
<p>Other fruits of MIT-Eni collaborations include research into carbon capture systems to be installed in cars, wearable technologies to improve workplace safety, energy storage, and the conversion of carbon dioxide into fuel.</p>
MIT Energy Initiative, Energy, Alternative energy, Renewable energy, Collaboration, Nuclear power and reactors, Nuclear science and engineering, Fusion, Plasma Science and Fusion Center, Research, School of Engineering, Physics, IndustryInsulator or superconductor? Physicists find graphene is bothhttp://news.mit.edu/2018/graphene-insulator-superconductor-0305
When rotated at a &quot;magic angle,&quot; graphene sheets can form an insulator or a superconductor.Mon, 05 Mar 2018 11:00:00 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2018/graphene-insulator-superconductor-0305<p>It’s hard to believe that a single material can be described by as many superlatives as graphene can. Since its discovery in 2004, scientists have found that the lacy, honeycomb-like sheet of carbon atoms — essentially the most microscopic shaving of pencil lead you can imagine — is not just the thinnest material known in the world, but also incredibly light and flexible, hundreds of times stronger than steel, and more electrically conductive than copper.</p>
<p>Now physicists at MIT and Harvard University have found the wonder material can exhibit even more curious electronic properties. In two papers published today in <em>Nature</em>, the team reports it can tune graphene to behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance.</p>
<p>Researchers in the past, including this team, have been able to synthesize graphene superconductors by placing the material in contact with other superconducting metals — an arrangement that allows graphene to inherit some superconducting behaviors. This time around, the team found a way to make graphene superconduct on its own, demonstrating that superconductivity can be an intrinsic quality in the purely carbon-based material.</p>
<p>The physicists accomplished this by creating a “superlattice” of two graphene sheets stacked together — not precisely on top of each other, but rotated ever so slightly, at a “magic angle” of 1.1 degrees. As a result, the overlaying, hexagonal honeycomb pattern is offset slightly, creating a precise moiré configuration that is predicted to induce strange, “strongly correlated interactions” between the electrons in the graphene sheets. In any other stacked configuration, graphene prefers to remain distinct, interacting very little, electronically or otherwise, with its neighboring layers.</p>
<p>The team, led by Pablo Jarillo-Herrero, an associate professor of physics at MIT, found that when rotated at the magic angle, the two sheets of graphene exhibit nonconducting behavior, similar to an exotic class of materials known as Mott insulators. When the researchers then applied voltage, adding small amounts of electrons to the graphene superlattice, they found that, at a certain level, the electrons broke out of the initial insulating state and flowed without resistance, as if through a superconductor.</p>
<p>“We can now use graphene as a new platform for investigating unconventional superconductivity,” Jarillo-Herrero says. “One can also imagine making a superconducting transistor out of graphene, which you can switch on and off, from superconducting to insulating. That opens many possibilities for quantum devices.”</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/magic-angle_0.gif" /></p>
<p><span style="font-size:10px;"><em>A large-scale interpretation of the moiré patterns formed when one graphene lattice is slightly rotated at a “magic angle,” with respect to a second graphene lattice.</em></span></p>
<p><strong>A 30-year gap</strong></p>
<p>A material’s ability to conduct electricity is normally represented in terms of energy bands. A single band represents a range of energies that a material’s electrons can have. There is an energy gap between bands, and when one band is filled, an electron must embody extra energy to overcome this gap, in order to occupy the next empty band.</p>
<p>A material is considered an insulator if the last occupied energy band is completely filled with electrons. Electrical conductors such as metals, on the other hand, exhibit partially filled energy bands, with empty energy states which the electrons can fill to freely move.</p>
<p>Mott insulators, however, are a class of materials that appear from their band structure to conduct electricity, but when measured, they behave as insulators. Specifically, their energy bands are half-filled, but because of strong electrostatic interactions between electrons (such as charges of equal sign repelling each other), the material does not conduct electricity. The half-filled band essentially splits into two miniature, almost-flat bands, with electrons completely occupying one band and leaving the other empty, and hence behaving as an insulator.</p>
<p>“This means all the electrons are blocked, so it’s an insulator because of this strong repulsion between the electrons, so nothing can flow,” Jarillo-Herrero explains. “Why are Mott insulators important? It turns out the parent compound of most high-temperature superconductors is a Mott insulator.”</p>
<p>In other words, scientists have found ways to manipulate the electronic properties of Mott insulators to turn them into superconductors, at relatively high temperatures of about 100 Kelvin. To do this, they chemically “dope” the material with oxygen, the atoms of which attract electrons out of the Mott insulator, leaving more room for remaining electrons to flow. When enough oxygen is added, the insulator morphs into a superconductor. How exactly this transition occurs, Jarillo-Herrero says, has been a 30-year mystery.</p>
<p>“This is a problem that is 30 years and counting, unsolved,” Jarillo-Herrero says. “These high-temperature superconductors have been studied to death, and they have many interesting behaviors. But we don’t know how to explain them.”</p>
<p><strong>A precise rotation</strong></p>
<p>Jarillo-Herrero and his colleagues looked for a simpler platform to study such unconventional physics. In studying the electronic properties in graphene, the team began to play around with simple stacks of graphene sheets. The researchers created two-sheet superlattices by first exfoliating a single flake of graphene from graphite, then carefully picking up half the flake with a glass slide coated with a sticky polymer and an insulating material of boron nitride.</p>
<p>They then rotated the glass slide very slightly and picked up the second half of the graphene flake, adhering it to the first half. In this way, they created a superlattice with an offset pattern that is distinct from graphene’s original honeycomb lattice.</p>
<p>The team repeated this experiment, creating several “devices,” or graphene superlattices, with various angles of rotation, between 0 and 3 degrees. They attached electrodes to each device and measured an electrical current passing through, then plotted the device’s resistance, given the amount of the original current that passed through.</p>
<p>“If you are off in your rotation angle by 0.2 degrees, all the physics is gone,” Jarillo-Herrero says. “No superconductivity or Mott insulator appears. So you have to be very precise with the alignment angle.”</p>
<p>At 1.1 degrees — a rotation that has been predicted to be a “magic angle” — the researchers found the graphene superlattice electronically resembled a flat band structure, similar to a Mott insulator, in which all electrons carry the same energy regardless of their momentum.</p>
<p>“Imagine the momentum for a car is mass times velocity,” Jarillo-Herrero says. “If you’re driving at 30 miles per hour, you have a certain amount of kinetic energy. If you drive at 60 miles per hour, you have much higher energy, and if you crash, you could deform a much bigger object. This thing is saying, no matter if you go 30 or 60 or 100 miles per hour, they would all have the same energy.”</p>
<p><strong>“Current for free”</strong></p>
<p>For electrons, this means that, even if they are occupying a half-filled energy band, one electron does not have any more energy than any other electron, to enable it to move around in that band. Therefore, even though such a half-filled band structure should act like a conductor, it instead behaves as an insulator — and more precisely, a Mott insulator.</p>
<p>This gave the team an idea: What if they could add electrons to these Mott-like superlattices, similar to how scientists doped Mott insulators with oxygen to turn them into superconductors? Would graphene assume superconducting qualities in turn?</p>
<p>To find out, they applied a small gate voltage to the “magic-angle graphene superlattice,” adding small amounts of electrons to the structure. As a result, individual electrons bound together with other electrons in graphene, allowing them to flow where before they could not. Throughout, the researchers continued to measure the electrical resistance of the material, and found that when they added a certain, small amount of electrons, the electrical current flowed without dissipating energy — just like a superconductor.</p>
<p>“You can flow current for free, no energy wasted, and this is showing graphene can be a superconductor,” Jarillo-Herrero says.</p>
<p>Perhaps more importantly, he says the researchers are able to tune graphene to behave as an insulator or a superconductor, and any phase in between, exhibiting all these diverse properties in one single device. This is in contrast to other methods, in which scientists have had to grow and manipulate hundreds of individual crystals, each of which can be made to behave in just one electronic phase.</p>
<p>“Usually, you have to grow different classes of materials to explore each phase,” Jarillo-Herrero says. “We’re doing this <em>in-situ</em>, in one shot, in a purely carbon device. We can explore all those physics in one device electrically, rather than having to make hundreds of devices. It couldn’t get any simpler.”</p>
<p>This research was supported in part by the Gordon and Betty Moore Foundation and ther National Science Foundation.</p>
Physicists at MIT and Harvard University have found that graphene, a lacy, honeycomb-like sheet of carbon atoms, can behave at two electrical extremes: as an insulator, in which electrons are completely blocked from flowing; and as a superconductor, in which electrical current can stream through without resistance. Courtesy of the researchersGraphene, Materials Science and Engineering, Physics, Quantum computing, Research, School of Science, Nanoscience and nanotechnologyJani Adcock and Drew Bent named Knight-Hennessy Scholarshttp://news.mit.edu/2018/jani-adcock-and-drew-bent-named-knight-hennessy-scholars-0301
Seniors will join class of 49 scholars in new fellowship program.Thu, 01 Mar 2018 14:50:01 -0500Julia Mongo | Office of Distinguished Fellowshipshttp://news.mit.edu/2018/jani-adcock-and-drew-bent-named-knight-hennessy-scholars-0301<p>Two MIT seniors, Jani Adcock and Drew Bent, will be part of this fall’s inaugural class of Knight-Hennessy Scholars. The fellowship funds the full cost of graduate education at Stanford University. Over 3,600 college seniors and recent graduates from around the world applied to this new program; 49 scholars from 20 countries were selected.</p>
<p>Knight-Hennessy Scholars aims to develop a community of future global leaders who can address complex challenges through collaboration and innovation. The fellowship is named for the 10th president of Stanford University, John L. Hennessy, and Nike Inc. co-founder and philanthropist Phil Knight, a Stanford alumnus who is contributing a $400 million endowment to the program.</p>
<p>Criteria for selection as a Knight-Hennessy Scholar include independence of thought, purposeful leadership, and a civic mindset. Applicants were also required to apply to and be admitted by the Stanford graduate program of their choice. In addition to funding for their academic studies, the Scholars will receive leadership training, mentorship, and experiential learning across multiple disciplines.</p>
<p><strong>Jani Adcock </strong>from Seattle, Washington, is a senior majoring in mechanical engineering with a minor in computer science. She aspires to develop numerical methods for more accurate and rapid simulations to open new avenues for renewable energy generation and efficient energy use. At the National Renewable Energy Laboratory, Adcock leveraged field data to improve a wind farm model; at Navigant Consulting, she assessed grid modernization efforts; at Tesla Motors, she analyzed vehicle data to improve reliability; and at Natel Energy, she designed components for a novel hydropower system. At MIT, she has served as an adviser for the student-run MIT Fall Career Fair, and as vice president of career development for MIT Society of Women Engineers. As a Knight-Hennessy Scholar, Adcock will pursue a PhD in computational and mathematical engineering at the Stanford School of Engineering.</p>
<p><strong>Drew Bent </strong>from Stanford, California, is a senior pursuing a double major in physics and electrical engineering and computer science. At MIT, Bent conducted research in the fields of economics and engineering, and was a features editor and reporter for <em>The Tech</em> newspaper. He interned at the White House Office of Science and Technology Policy, Bridgewater Associates, Khan Academy, and Sony Ericsson, and was a consultant at the World Bank. Through MISTI’s Global Teaching Labs, he taught high school physics in in Crema, Italy. Bent aspires to work at an education startup to develop new types of K-12 schools in California, and ultimately reform education policy through public office at the national level. As a Knight-Hennessy Scholar, Bent will embark on a master’s degree in policy, organization, and leadership studies at the Stanford Graduate School of Education.</p>
<p>“Jani and Drew are remarkable students, who will greatly benefit from the new Knight-Hennessy program,” says Kimberly Benard, assistant dean for distinguished fellowships and academic excellence in MIT's Office of Undergraduate Advising and Academic Programming. “They are both innovators who plan to use their combined MIT and Stanford educations to improve the world through renewable energy and educational initiatives, respectively.”</p>
Jani Adcock and Drew BentPhotos courtesy of Knight-Hennessy ScholarsUndergraduate, Awards, honors and fellowships, Mechanical engineering, Electrical Engineering & Computer Science (eecs), Physics, Students, MISTI, Women in STEMAstronomers detect earliest evidence yet of hydrogen in the universehttp://news.mit.edu/2018/astronomers-detect-earliest-evidence-yet-hydrogen-universe-0228
Emitted just 180 million years after Big Bang, signal indicates universe was much colder than expected.Wed, 28 Feb 2018 12:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2018/astronomers-detect-earliest-evidence-yet-hydrogen-universe-0228<p>In a study published today in the journal <em>Nature</em>, astronomers from MIT and Arizona State University report that a table-sized radio antenna in a remote region of western Australia has picked up faint signals of hydrogen gas from the primordial universe.</p>
<p>The scientists have traced the signals to just 180 million years after the Big Bang, making the detection the earliest evidence of hydrogen yet observed.</p>
<p>They also determined that the gas was in a state that would have been possible only in the presence of the very first stars. These stars, blinking on for the first time in a universe that was previously devoid of light, emitted ultraviolet radiation that interacted with the surrounding hydrogen gas. As a result, hydrogen atoms across the universe began to absorb background radiation — a pivotal change that the scientists were able to detect in the form of radio waves.</p>
<p>The findings provide evidence that the first stars may have started turning on around 180 million years after the Big Bang.</p>
<p>“This is the first real signal that stars are starting to form, and starting to affect the medium around them,” says study co-author Alan Rogers, a scientist at MIT’s Haystack Observatory. “What’s happening in this period is that some of the radiation from the very first stars is starting to allow hydrogen to be seen. It’s causing hydrogen to start absorbing the background radiation, so you start seeing it in silhouette, at particular radio frequencies.”</p>
<div class="cms-placeholder-content-video"></div>
<p>Certain characteristics in the detected radio waves also suggest that hydrogen gas, and the universe as a whole, must have been twice as cold as scientists previously estimated, with a temperature of about 3 kelvins, or –454 degrees Fahrenheit. Rogers and his colleagues are unsure precisely why the early universe was so much colder, but some researchers have suggested that interactions with dark matter may have played some role.</p>
<p>“These results require some changes in our current understanding of the early evolution of the universe,” says Colin Lonsdale, director of Haystack Observatory. “It would affect cosmological models and require theorists to put their thinking caps back on to figure out how that would happen.”</p>
<p>Rogers’ co-authors are lead author Judd Bowman of Arizona State University (ASU), along with Thomas Mozdzen, Nivedita Mahesh, and Raul Monsalve, from the University of Colorado.</p>
<p><strong>Turning on, tuning in</strong></p>
<p>The scientists detected the primordial hydrogen gas using EDGES (Experiment to Detect Global EoR Signature), a small ground-based radio antenna located in western Australia, and funded by the National Science Foundation.</p>
<p>The antennas and portions of the receiver were designed and constructed by Rogers and the Haystack Observatory team; Bowman, Monsalve, and the ASU team added an automated antenna reflection measurement system to the receiver, outfitted a control hut with the electronics, constructed the ground plane, and conducted the field work for the project. Australia’s Commonwealth Scientific and Industrial Research Organization provided on-site infrastructure for the EDGES project.</p>
<p>The current version of EDGES is the result of years of design iteration and instrument calibration in order to reach the levels of precision necessary for successfully achieving an extremely difficult measurement.</p>
<p>The instrument was originally designed to pick up radio waves emitted from a time in the universe’s history known as the Epoch of Reionization, or EoR. During this period, it’s thought that the first luminous sources, such as stars, quasars, and galaxies, appeared in the universe, causing the previously neutral intergalactic medium, made mostly of hydrogen gas, to become ionized.</p>
<p>Prior to the appearance of the first stars, the universe was shrouded in darkness, and hydrogen, its most abundant element, was virtually invisible, embodying an energy state that was indistinguishable from the surrounding cosmic background radiation.</p>
<p>Scientists believe that when the first stars turned on, they provided ultraviolet radiation that caused changes to the hydrogen atoms’ distribution of energy states. These changes induced hydrogen’s single electron to spin in alignment or opposite to the spin of its proton, causing hydrogen as a whole to “decouple” from the background radiation. As a result, hydrogen gas began to either emit or absorb that radiation, at a characteristic wavelength of 21 centimeters, equivalent to a frequency of 1,420 megahertz. As the universe expanded over time, this radiation became “red-shifted” to lower frequencies. By the time this 21-centimeter radiation reached present-day Earth, it landed somewhere in the range of 100 megahertz.</p>
<p>Rogers and his colleagues have been using EDGES to try to detect hydrogen that existed during the very early evolution of the universe, in order to pinpoint when the first stars turned on.</p>
<p>“There is a great technical challenge to making this detection,” says Peter Kurczynski, program director for Advanced Technologies and Instrumentation, in the Division of Astronomical Sciences at the National Science Foundation, which has provided funding for the project over the past several years. “Sources of noise can be a thousand times brighter than the signal they are looking for. It is like being in the middle of a hurricane and trying to hear the flap of a hummingbird’s wing.”</p>
<p>The instrument, about the size of a small table, sits in a remote region of western Australia where there are very little humanmade radio signals to interfere with incoming radio waves from the distant universe. The antenna detects radio waves from the entire sky, and the researchers had originally tuned it to listen in at a frequency range of 100 to 200 megahertz.</p>
<p><strong>A switch hit </strong></p>
<p>However, when the researchers looked within this range, they initially failed to pick up much of any signal. They realized that theoretical models had predicted that primordial hydrogen should give off emissions within this range if the gas was hotter than the surrounding medium. But what if the gas was in fact colder? Models predict that the hydrogen should then absorb radiation more strongly in the 50 to 100 megahertz frequency range.</p>
<p>“As soon as we switched our system to this lower range, we started seeing things that we felt might be a real signature,” Rogers says.</p>
<p>Specifically, the researchers observed a flattened absorption profile, or a dip in the radio waves, at around 78 megahertz.</p>
<p>“We see this dip most strongly at about 78 megahertz, and that frequency corresponds to roughly 180 million years after the Big Bang,” Rogers says. “In terms of a direct detection of a signal from the hydrogen gas itself, this has got to be the earliest.”</p>
<p>The dip in radio waves was stronger and deeper than theoretical models predicted, suggesting that the hydrogen gas at the time was colder than previously thought. The radio waves’ profile also matches theoretical predictions of what would be produced if hydrogen were indeed influenced by the first stars.</p>
<p>“The signature of this absorption feature is uniquely associated with the first stars,” Lonsdale says. “Those stars are the most plausible source of radiation that would produce this signal.”</p>
<p>“It is unlikely that we’ll be able to see any earlier into the history of stars in our lifetimes,” lead author Bowman of ASU says. “This project shows that a promising new technique can work and has paved the way for decades of new astrophysical discoveries.”</p>
<p>The researchers say this new detection lifts the curtain on a previously obscure phase in the evolution of the universe.</p>
<p>“This is exciting because it is the first look into a particularly important period in the universe, when the first stars and galaxies were beginning to form,” Lonsdale says. “This is the first time anybody’s had any direct observational data from that epoch.”</p>
<p>This research was supported by funding from the National Science Foundation.</p>
Artist's rendering of the universe's first, massive, blue stars in gaseous filaments, with the cosmic microwave background (CMB) at the edges. Using radio observations of the distant universe, NSF-funded researchers Judd Bowman of Arizona State University, Alan Rogers of MIT, and others discovered the influence of such early stars on primordial gas. The team inferred the stars' presence from dimming of the CMB, a result of the gaseous filaments absorbing the stars' UV light. The CMB is dimmer than expected, indicating the filaments may have been colder than expected, possibly from interactions with dark matter. Image: N.R.Fuller/National Science FoundationAstronomy, Astrophysics, Haystack Observatory, Physics, Research, School of Science, space, Space, astronomy and planetary science, National Science Foundation (NSF)MIT rates No. 1 in 12 subjects in 2018 QS World University Rankingshttp://news.mit.edu/2018/mit-no-1-2018-qs-world-university-rankings-subjects-0228
MIT ranked within top 5 in 19 out of 48 subject areas.
Wed, 28 Feb 2018 12:00:01 -0500Stephanie Eich | Resource Developmenthttp://news.mit.edu/2018/mit-no-1-2018-qs-world-university-rankings-subjects-0228<p>MIT has been honored with 12 No. 1 subject rankings in the QS World University Rankings for 2018.</p>
<p>MIT received a No. 1 ranking in the following QS subject areas: Architecture/Built Environment; Linguistics; Chemical Engineering; Civil and Structural Engineering; Computer Science and Information Systems; Electrical and Electronic Engineering; Mechanical, Aeronautical and Manufacturing Engineering; Chemistry; Materials Science; Mathematics; Physics and Astronomy; and Statistics and Operational Research. &nbsp;&nbsp;</p>
<p>Additional high-ranking MIT subjects include: Art and Design (No. 4), Biological Sciences (No. 2), Earth and Marine Sciences (No. 3), Environmental Sciences (No. 3), Accounting and Finance (No. 2), Business and Management Studies (No. 4), and Economics and Econometrics (No. 2).</p>
<p>Quacquarelli Symonds Limited subject rankings, published annually, are designed to help prospective students find the leading schools in their field of interest. Rankings cover 48 disciplines and are based on an institute’s research quality and accomplishments, academic reputation, and graduate employment.</p>
<p>MIT has been ranked as the No. 1 university in the world by QS World University Rankings for six&nbsp;straight years.</p>
Photo: Patrick GilloolyRankings, Computer science and technology, Linguistics, Chemical engineering, Civil and environmental engineering, Mechanical engineering, Chemistry, Materials science, Mathematics, Physics, Economics, Design, EAPS, Business and management, Accounting, Finance, DMSE, School of Engineering, School of Science, School of Architecture and Planning, Sloan School of Management, SHASS, Electrical Engineering & Computer Science (eecs), ArchitectureMIT physicists observe electroweak production of same-sign W boson pairshttp://news.mit.edu/2018/mit-physicists-observe-electroweak-production-same-sign-w-boson-pairs-cms-0227
With the aid of the Compact Muon Solenid detector at the Large Hadron Collider, a Laboratory for Nuclear Science-led group seeks to further understand the building blocks of matter.Tue, 27 Feb 2018 16:30:00 -0500Scott Morley | Laboratory for Nuclear Sciencehttp://news.mit.edu/2018/mit-physicists-observe-electroweak-production-same-sign-w-boson-pairs-cms-0227<p>In research conducted by a group led by MIT Laboratory for Nuclear Science researcher and associate professor of physics Markus Klute, electroweak productions of same-sign W boson pairs were observed, the first such observation of its kind and a milestone toward precision testing of vector boson scattering (W and Z bosons) at the Large Hadron Collider (LHC).</p>
<p>The LHC at CERN in Geneva, Switzerland, was proposed in the 1980s as a machine to either find the Higgs boson or discover yet unknown particles or interactions. This idea, that the LHC would be able to make a discovery, whatever that might be, is called by theorists No-lose Theorem, and is connected to probing the scattering of W boson pairs at energies above 1 teraelectronvolt (TeV). In 2012, only two years after the first high-energy collision at the LHC, this proposal paid huge dividends when the Higgs boson was discovered by the ATLAS and&nbsp;Compact Muon Solenid (CMS) collaborations.</p>
<p>According to CERN, the CMS detector at the LHC utilizes a massive solenoid magnet to study everything from the Higgs boson to dark matter to the Standard Model. CMS is capable of generating a magnetic field that is approximately 100,000 times that of Earth. It resides in an underground cavern near Cessy, France, which is northwest of Geneva.</p>
<p>The main goal of a recent measurement by CMS was to identify W boson pairs with the same sign (W+W+ or W-W-) produced purely via the electroweak interaction and probing the scattering of W bosons. The result does not unveil physics beyond the Standard Model, but&nbsp;this&nbsp;first observation of this process&nbsp;marks a starting point for a field of study to independently test whether the discovered Higgs boson is or is not the particle predicted by Robert Brout, François Englert,&nbsp;and Peter Higgs. It is anticipated that the rapidly growing data sets available at the LHC will further knowledge along these lines. Studies show that the high luminosity LHC will likely allow the direct study of longitudinal W boson scattering.</p>
<p>“The measurement of vector-boson scattering processes, like the one studied in this paper, is an important test bench of the nature of the Higgs boson, as small deviations from the Standard Model expectation can have a large impact on event rates,” Klute says. “While challenging new physics models, these processes also allow a unique model-independent measurement of Higgs boson couplings to the W and Z boson at the LHC.”</p>
<p>“The observation of this vector-boson scattering process is an important milestone toward future precision measurements,” Klute says. “These measurements are very challenging experimentally and require theoretical predictions with high precision. Both areas are pushed forward by the published results.”</p>
<p>The work, while within CMS, was performed by MIT and included Klute, his students Andrew Levin and Xinmei Nui, and research scientist Guillelmo Gomez-Ceballos, along with University of Antwerp colleague Xavier Janssen and his student Jasper Lauwers.</p>
<p>The work has been published in <em><a href="https://dx.doi.org/10.1103/PhysRevLett.120.081801" target="_blank">Physical Review Letters</a></em>.</p>
<p>This research was funded with support from U.S. Department of Energy.</p>
Vector-boson scattering processes are characterized by two high-energetic jets in the forward regions of the detector. The Figure shows a significant excess of events in the distribution of the mass of the two tagging jets in yellow, labelled as EW WW.Image: Markus KluteLaboratory for Nuclear Science, Research, Higgs boson, Physics, School of Science, Particles, CERN, Standard Model of particle physics, Profiles, Nuclear science and engineeringUrban heat island effects depend on a city’s layouthttp://news.mit.edu/2018/urban-heat-island-effects-depend-city-layout-0222
The way streets and buildings are arranged makes a big difference in how heat builds up, study shows.Thu, 22 Feb 2018 00:00:02 -0500David L. Chandler | MIT News Officehttp://news.mit.edu/2018/urban-heat-island-effects-depend-city-layout-0222<p>The arrangement of a city’s streets and buildings plays a crucial role in the local urban heat island effect, which causes cities to be hotter than their surroundings, researchers have found. The new finding could provide city planners and officials with new ways to influence those effects.</p>
<p>Some cities, such as New York and Chicago, are laid out on a precise grid, like the atoms in a crystal, while others such as Boston or London are arranged more chaotically, like the disordered atoms in a liquid or glass. The researchers found that the “crystalline” cities had a far greater buildup of heat compared to their surroundings than did the “glass-like” ones.</p>
<p>The study, published today in the journal <em>Physical Review Letters</em>, found these differences in city patterns, which they call “texture,” was the most important determinant of a city’s heat island effect. The research was carried out by MIT and National Center for Scientific Research senior research scientist Roland Pellenq, who is also director of a joint MIT/ CNRS/Aix-Marseille University laboratory called <em>&lt;MSE&gt;</em><sup>2</sup> (MultiScale Material Science for Energy and Environment); professor of civil and environmental engineering Franz-Josef Ulm; research assistant Jacob Sobstyl; <em>&lt;MSE&gt;</em><sup>2</sup> senior research scientist T. Emig; and M.J. Abdolhosseini Qomi, assistant professor of civil and environmental engineering at the University of California at Irvine.</p>
<p>The heat island effect has been known for decades. It essentially results from the fact that urban building materials, such as concrete and asphalt, can absorb heat during the day and radiate it back at night, much more than areas covered with vegetation do. The effect can be quite dramatic, adding as much as 10 degrees Farenheit to night-time temperatures in places such as Phoenix, Arizona. In such places this effect can significantly increase health problems and energy use during hot weather, so a better understanding of what produces it will be important in an era when ever more people are living in cities.</p>
<p>The team found that using mathematical models that were developed to analyze atomic structures in materials provides a useful tool, leading to a straightforward formula to describe the way a city’s design would influence its heat-island effect, Pellenq says.</p>
<p>“We use tools of classical statistical physics,” he explains. The researchers adapted formulas initially devised to describe how individual atoms in a material are affected by forces from the other atoms, and they reduced these complex sets of relationships to much simpler statistical descriptions of the relative distances of nearby buildings to each other. They then applied them to patterns of buildings determined from satellite images of 47 cities in the U.S. and other countries, ultimately ending up with a single index number for each — called the local order parameter — ranging between 0 (total disorder) and 1 (perfect crystalline structure), to provide a statistical description of the cluster of nearest neighbors of any given building.</p>
<p>For each city, they had to collect reliable temperature data, which came from one station within the city and another outside it but nearby, and then determine the difference.</p>
<p>To calculate this local order parameter, physicists typically have to use methods such as bombarding materials with neutrons to locate the positions of atoms within them. But for this project, Pellenq says, “to get the building positions we don’t use neutrons, just Google maps.” Using algorithms they developed to determine the parameter from the city maps, they found that the cities varied from 0.5 to 0.9.</p>
<p>The differences in the heating effect seem to result from the way buildings reradiate heat that can then be reabsorbed by other buildings that face them directly, the team determined.</p>
<p>Especially for places such as China where new cities are rapidly being built, and other regions where existing cities are expanding rapidly, the information could be important to have, he says. In hot locations, cities could be designed to minimize the extra heating, but in colder places the effect might actually be an advantage, and cities could be designed accordingly.</p>
<p>“If you’re planning a new section of Phoenix,” Pellenq says, “you don’t want to build on a grid, since it’s already a very hot place. But somewhere in Canada, a mayor may say no, we’ll choose to use the grid, to keep the city warmer.”</p>
<p>The effects are significant, he says. The team evaluated all the states individually and found, for example, that in the state of Florida alone urban heat island effects cause an estimated $400 million in excess costs for air conditioning. “This gives a strategy for urban planners,” he says. While in general it’s simpler to follow a grid pattern, in terms of placing utility lines, sewer and water pipes, and transportation systems, in places where heat can be a serious issue, it can be well worth the extra complications for a less linear layout.</p>
<p>This study also suggests that research on construction materials may offer a way forward to properly manage heat interaction between buildings in cities’ historical downtown areas.</p>
<p>The work was partly supported by the Concrete Sustainability Hub at MIT, sponsored by the Portland Cement Association and the Ready-Mixed Concrete Research and Education Foundation.</p>
A new study found that cities with an orderly pattern, like the street grid seen in most of this map, have a much greater urban heat island effect than those with a more disorderly pattern, such as areas in the upper right.
Courtesy of the researchersResearch, Architecture, Physics, Civil and environmental engineering, Cities, Urban studies and planning, Climate, Climate change, Global Warming, Energy, Development, School of EngineeringPhysicists create new form of lighthttp://news.mit.edu/2018/physicists-create-new-form-light-0215
Newly observed optical state could enable quantum computing with photons.Thu, 15 Feb 2018 13:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2018/physicists-create-new-form-light-0215<p>Try a quick experiment: Take two flashlights into a dark room and shine them so that their light beams cross. Notice anything peculiar? The rather anticlimactic answer is, probably not. That’s because the individual photons that make up light do not interact. Instead, they simply pass each other by, like indifferent spirits in the night.</p>
<p>But what if light particles could be made to interact, attracting and repelling each other like atoms in ordinary matter? One tantalizing, albeit sci-fi possibility: light sabers — beams of light that can pull and push on each other, making for dazzling, epic confrontations. Or, in a more likely scenario, two beams of light could meet and merge into one single, luminous stream.</p>
<p>It may seem like such optical behavior would require bending the rules of physics, but in fact, scientists at MIT, Harvard University, and elsewhere have now demonstrated that photons can indeed be made to interact — an accomplishment that could open a path toward using photons in quantum computing, if not in light sabers.</p>
<p>In a paper published today in the journal <em>Science</em>, the team, led by Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT, and Professor Mikhail Lukin from Harvard University, reports that it has observed groups of three photons interacting and, in effect, sticking together to form a completely new kind of photonic matter.</p>
<p>In controlled experiments, the researchers found that when they shone a very weak laser beam through a dense cloud of ultracold rubidium atoms, rather than exiting the cloud as single, randomly spaced photons, the photons bound together in pairs or triplets, suggesting some kind of interaction — in this case, attraction — taking place among them.</p>
<p>While photons normally have no mass and travel at 300,000 kilometers per second (the speed of light), the researchers found that the bound photons actually acquired a fraction of an electron’s mass. These newly weighed-down light particles were also relatively sluggish, traveling about 100,000 times slower than normal noninteracting photons.</p>
<p>Vuletic says the results demonstrate that photons can indeed attract, or entangle each other. If they can be made to interact in other ways, photons may be harnessed to perform extremely fast, incredibly complex quantum computations.</p>
<p>“The interaction of individual photons has been a very long dream for decades,” Vuletic says.</p>
<p>Vuletic’s co-authors include Qi-Yung Liang, Sergio Cantu, and Travis Nicholson from MIT, Lukin and Aditya Venkatramani of Harvard, Michael Gullans and Alexey Gorshkov of the University of Maryland, Jeff Thompson from Princeton University, and Cheng Ching of the University of Chicago.</p>
<p><strong>Biggering and biggering</strong></p>
<p>Vuletic and Lukin lead the MIT-Harvard Center for Ultracold Atoms, and together they have been looking for ways, both theoretical and experimental, to encourage interactions between photons. In 2013, the effort paid off, as the team observed pairs of photons interacting and binding together for the first time, creating an entirely new state of matter.</p>
<p>In their new work, the researchers wondered whether interactions could take place between not only two photons, but more.</p>
<p>“For example, you can combine oxygen molecules to form O<sub>2</sub> and O<sub>3</sub> (ozone), but not O<sub>4</sub>, and for some molecules you can’t form even a three-particle molecule,” Vuletic says. “So it was an open question: Can you add more photons to a molecule to make bigger and bigger things?”</p>
<p>To find out, the team used the same experimental approach they used to observe two-photon interactions. The process begins with cooling a cloud of rubidium atoms to ultracold temperatures, just a millionth of a degree above absolute zero. Cooling the atoms slows them to a near standstill. Through this cloud of immobilized atoms, the researchers then shine a very weak laser beam — so weak, in fact, that only a handful of photons travel through the cloud at any one time.</p>
<p>The researchers then measure the photons as they come out the other side of the atom cloud. In the new experiment, they found that the photons streamed out as pairs and triplets, rather than exiting the cloud at random intervals, as single photons having nothing to do with each other.</p>
<p>In addition to tracking the number and rate of photons, the team measured the phase of photons, before and after traveling through the atom cloud. A photon’s phase indicates its frequency of oscillation.</p>
<p>“The phase tells you how strongly they’re interacting, and the larger the phase, the stronger they are bound together,” Venkatramani explains. The team observed that as three-photon particles exited the atom cloud simultaneously, their phase was shifted compared to what it was when the photons didn’t interact at all, and was three times larger than the phase shift of two-photon molecules. “This means these photons are not just each of them independently interacting, but they’re all together interacting strongly.”</p>
<p><strong>Memorable encounters</strong></p>
<p>The researchers then developed a hypothesis to explain what might have caused the photons to interact in the first place. Their model, based on physical principles, puts forth the following scenario: As a single photon moves through the cloud of rubidium atoms, it briefly lands on a nearby atom before skipping to another atom, like a bee flitting between flowers, until it reaches the other end.</p>
<p>If another photon is simultaneously traveling through the cloud, it can also spend some time on a rubidium atom, forming a polariton — a hybrid that is part photon, part atom. Then two polaritons can interact with each other via their atomic component. At the edge of the cloud, the atoms remain where they are, while the photons exit, still bound together. The researchers found that this same phenomenon can occur with three photons, forming an even stronger bond than the interactions between two photons.</p>
<p>“What was interesting was that these triplets formed at all,” Vuletic says. “It was also not known whether they would be equally, less, or more strongly bound compared with photon pairs.”</p>
<p>The entire interaction within the atom cloud occurs over a millionth of a second. And it is this interaction that triggers photons to remain bound together, even after they’ve left the cloud.</p>
<p>“What’s neat about this is, when photons go through the medium, anything that happens in the medium, they ‘remember’ when they get out,” Cantu says.</p>
<p>This means that photons that have interacted with each other, in this case through an attraction between them, can be thought of as strongly correlated, or entangled — a key property for any quantum computing bit.</p>
<p>“Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers,” Vuletic says. “If photons can influence one another, then if you can entangle these photons, and we’ve done that, you can use them to distribute quantum information in an interesting and useful way.”</p>
<p>Going forward, the team will look for ways to coerce other interactions such as repulsion, where photons may scatter off each other like billiard balls.</p>
<p>“It’s completely novel in the sense that we don’t even know sometimes qualitatively what to expect,” Vuletic says. “With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light? Or will something else happen? It’s very uncharted territory.”</p>
<p>This research was supported in part by the National Science Foundation.</p>
Scientists at MIT, Harvard University, and elsewhere have now demonstrated that photons can be made to interact — an accomplishment that could open a path toward using photons in quantum computing, if not in light sabers.
Image: Christine Daniloff/MITPhysics, Quantum computing, Research, Research Laboratory of Electronics, School of Science, Photonics, National Science Foundation (NSF)Chaos and climate: Celebrating two pioneers of modern meteorologyhttp://news.mit.edu/2018/mit-chaos-and-climate-celebration-two-pioneers-modern-meteorology-0214
Trailblazing scientists Jule Charney and Edward Lorenz gave us numerical weather prediction and chaos theory, highlighting the value of basic research.Wed, 14 Feb 2018 13:30:00 -0500Lauren Hinkel | Oceans at MIThttp://news.mit.edu/2018/mit-chaos-and-climate-celebration-two-pioneers-modern-meteorology-0214<p>Our understanding of atmospheric and climate dynamics, as well as weather prediction and its limits, would not be what it is today without advances in the fundamental science of modern meteorology that took place at MIT in the post WWII era. Much of this is thanks to two prominent MIT meteorologists born a hundred years ago, but whose work is very much relevant today.</p>
<p>Earlier this month, the Department of Earth, Atmospheric and Planetary Sciences (<a href="http://eapsweb.mit.edu/">EAPS</a>) celebrated the lives and scientific legacies of these two former MIT professors, Edward Norton Lorenz and Jule Gregory Charney, during a two-day symposium:&nbsp;<a href="http://paocweb.mit.edu/about/paoc-spotlights/mit-on-chaos-and-climate">MIT on Chaos and Climate</a>. The event was organized by EAPS faculty from the&nbsp;<a href="http://lorenz.mit.edu/">Lorenz Center</a>&nbsp;and the Program in Atmospheres, Oceans and Climate (PAOC), marking the centennial of the scientists’ birth.</p>
<p>The department brought together the MIT community and friends and welcomed back alumni, and former faculty and scientists from EAPS and the former Department of Meteorology (Course XIX). Also invited were respected colleagues from many scientific fields affected by the work of Charney and Lorenz, including oceanography, meteorology, physics, applied mathematics, and climate science. Together, the group composed of biological and professional families shared vignettes and personal testimonials of the scientists on the first day, and discussed the broader impacts that Charney and Lorenz’s research had on the department and the broader community on the second.</p>
<p><strong>Meteorology’s origins at MIT</strong></p>
<p>Charney and Lorenz were members and chairs of the former Department of Meteorology, which emerged from the country’s first meteorology program founded at MIT by Carl-Gustaf Rossby, considered one of the founders of modern meteorology. In 1983, the department merged with Course XII to become the current EAPS, and was the forefather of PAOC.</p>
<p>The pioneering work of Charney and Lorenz heralded the field of modern meteorology. “It’s fair to say that Jule Charney turned the mystery of the erratic behavior of the atmosphere into a recognizable, although a very, very difficult problem in fluid physics,” said Joe Pedlosky, Woods Hole Oceanographic Institution Emeritus Senior Scientist, on the symposium’s second day.</p>
<p>Charney’s quasi-geostrophic vorticity equations allowed for concise mathematical description of large-scale atmospheric and oceanic circulations, enabling the numerical weather prediction. Among this and his many fundamental contributions to the field, Charney identified “baroclinic instability,” the mechanism that explains the size, structure, and growth rate of mid-latitude weather systems, and is a ubiquitous phenomenon in rotating, stratified fluids like our oceans and atmosphere. His innovative research provided insights to the theories of weather systems, hydro-dynamical instability, atmospheric wave propagation, hurricanes, drought, desertification, atmospheric blocking, and ocean currents. Many felt the pull of his charisma and academic integrity, falling into “orbit around the Charney sun.” This, along with his idealism and quest for fascinating research results, was the driving force behind many national and international weather initiatives and programs.</p>
<p>“Being in the room with Charney was like being in the room with a tiger, a very friendly tiger,” said David Randall, University Distinguished Professor at Colorado State University.</p>
<p>Lorenz could be considered Charney’s department foil. Many described him as a quiet, humble soul, and in Charney’s words as remembered by Pedlosky, “Lorenz is a genius with a soul of an artist.”</p>
<p>He revolutionized our understanding of atmospheric dynamics and circulation through research into the energetics of stratified, rotating fluids. In “one of the greatest intellectual advances of our time,” Lorenz set out to show that statistical long-range weather forecasting did not perform as well as numerical forecasting, and in the process observed “deterministic chaos,” facts that were&nbsp;highlighted by talks from Kerry Emanuel, the MIT Cecil and Ida Green Professor of Atmospheric Science and co-director of the Lorenz Center, and Tim Palmer, the Royal Society Research Professor at the University of Oxford.</p>
<p>Lorenz’s meticulous research found that infinitesimal differences in initial conditions produced dramatically different forecasts. Chaos theory, popularized as the butterfly effect,&nbsp;shifted our thinking away from deterministic numerical weather prediction to more probabilistic forecasts. “History may well record that Ed Lorenz had hammered the last nail into the coffin of the Cartesian universe,” Emanuel said. Despite the fact that the results of Charney and Lorenz’s research were largely opposing, Palmer noted that their work is now seamlessly intertwined for the benefit of science and society.</p>
<p><strong>Ripples in weather, climate, and beyond earth science</strong></p>
<p>The symposium, through formal and informal presentations, painted a picture of what meteorology was like under the leadership of Lorenz and Charney, and their influence on other fields of study.</p>
<p>On the symposium’s first day, alumni, colleagues, friends, and family shared personal stories of encounters with Charney and Lorenz, including anecdotes about lesser known research and affiliations like Charney’s work with the Union of Concerned Scientists, the discovery of chaos and the jetstream, the study of storm surge in Venice, and MIT’s connection with meteorology in Italy. Mankin Mak, alum of Lorenz’s group and Professor Emeritus at the Department of Atmospheric Sciences at the University of Illinois, even named the “Charney number” after the scientist. All the while, the camaraderie between the Course XIX alumni and excitement to be back in EAPS was palpable, spilling over into the evening’s dinner and the following day.</p>
<p>The second part of the symposium opened to the public and focused on the influence of Lorenz and Charney’s research. This included talks on cloud aggregation, hydrology and atmospheric coupling leading to desertification, oceanography and a realistic model of the Gulf Stream, observation of the turbulent cascade in nonlinear systems, CO2-related climate change, chaos in our solar system, fluid dynamics of pathogen transmission, tipping points in population dynamics, and more.</p>
<p>First-day attendees experienced the extent of the researchers’ work through multimedia. While a slideshow of Lorenz and Charney played, EAPS graduate students&nbsp;Brian Green,&nbsp;Mukund Gupta,&nbsp;Megan Lickley&nbsp;and&nbsp;Santiago Benavides, as well as postdocs&nbsp;Ed Doddridge,&nbsp;Jon Lauderdale,&nbsp;Chris Follett, and&nbsp;Daniel Koll&nbsp;shared posters of their own research during the morning of the symposium’s first day. Two displays were unveiled, which would be hung outside the EAPS Charney Library, across from Charney’s old office on the 14th floor where this groundbreaking work took place, and on the 18th floor. Lab assistant&nbsp;Bill McKenna&nbsp;set up a replica of the LGP-30 computer and printer that Lorenz used for his renowned calculations and showed how it would have been used. Short films from&nbsp;Meg Rosenberg, a producer and editor at MIT Video Productions, and&nbsp;Josh Kastorf, from the Earth Resources Laboratory in EAPS, established timelines of Lorenz and Charney’s life and work at MIT, and explained the origins and implications of chaos theory, respectively.</p>
<p>Charney had once remarked that a “scientist’s interest in the history of his own field was the first sign of senility,” but Raffaele Ferrari, the EAPS Cecil and Ida Green Professor of Oceanography and chair of PAOC, believes that revisiting the past can provide valuable lessons for future thinking and research. “For the students, it must have been inspirational and helpful to see where this department comes from,” Ferrari says. “You realize [that] the history of this department is quite impressive … and the people were here that created this field. … There is no other department like that, definitely [not] in meteorology, that has ever achieved that kind of leadership intellectually on every level.”</p>
<p>By revisiting the group’s history, students could see the evolution of scientific ideas and the values that made the department what it was and that became part of its legacy. In a sentiment echoed by keynote speaker Ernest Moniz, the MIT Cecil and Ida Green Professor Emeritus of Physics and Engineering Systems and special advisor to the MIT President, basic research is the lifeblood of a successful society in the long-term. “[Lorenz and Charney were] thinking about the fundamentals of the problem with students here at MIT,” he said. This practice of fostering curiosity-driven research now underpins the mission of the Lorenz Center: to understand and predict global climate change. “And [that’s] always that you want —&nbsp;to fundamentally understand the problem and then as a result you can make an impact on the real world, on practical applications.”</p>
<p>EAPS professors&nbsp;Ferrari, Emanuel,&nbsp;John Marshall&nbsp;(event MC), Paola Rizzoli,&nbsp;and&nbsp;Dan Rothman&nbsp;organized the symposium. The&nbsp;event was sponsored by the Henry Houghton Fund and the Lorenz Center within EAPS.</p>
<p>Those interested in making&nbsp;a contribution to the Lorenz Center Fund, or to support the renovation of the Charney Library, can contact&nbsp;<a href="http://xeapsweb.mit.edu/people/ellis-angela">Angela Ellis</a>&nbsp;at 617-253-5796 or via email:&nbsp;<a href="mailto:aellis@mit.edu">aellis@mit.edu</a>.</p>
Robert van der Hilst moderates the symposium's day-two panel consisting of Sir Brian Hoskins, Inez Fung, Kerry Emanuel, Allison Wing and John Bush.Photo: Lauren HinkelClimate, Climate change, Oceanography and ocean engineering, School of Science, Earth and atmospheric sciences, EAPS, Lorenz Center, Special events and guest speakers, PhysicsGiving everyone a window into the human bodyhttp://news.mit.edu/2018/startup-butterfly-network-ultrasound-smartphone-0207
Startup’s low-cost, portable scanner generates clinical-quality ultrasounds on a smartphone.Tue, 06 Feb 2018 23:59:59 -0500Rob Matheson | MIT News Officehttp://news.mit.edu/2018/startup-butterfly-network-ultrasound-smartphone-0207
<p>Butterfly Network, a startup co-founded by an MIT alumnus, aims to make ultrasound imaging as simple and ubiquitous as blood-pressure or temperature checks — in hospitals and, eventually, in consumers’ homes.</p>
<p>The startup has developed a low-cost, handheld scanner, based in part on work done by co-founder Nevada Sanchez ’10, SM ’11, that generates clinical-quality ultrasounds on a smartphone. Ultrasounds are uploaded to the cloud, where any expert with permission can give second opinions or help analyze images.</p>
<p>By making ultrasound imaging more ubiquitous, the co-founders aim to help health care professionals more quickly generate life-saving diagnoses.</p>
<p>Traditional ultrasound machines rely on vibrating crystals and other components to produce ultrasound images. These are generally large, stationary machines that cost anywhere from $15,000 to $100,000. But the startup’s device, called iQ, which resembles an electric razor that plugs into an iPhone lightning jack, essentially puts an entire ultrasound system on a chip, meaning it’s portable and sells for about $2,000.</p>
<p>In November, the U.S. Food and Drug Administration cleared the device for numerous clinical applications, including urological, abdominal, cardiovascular, fetal, gynecological, and musculo-skeletal. Tens of thousands of orders have been placed and will be shipped over the next few months.</p>
<p>“First users will be doctors and clinicians who are more comfortable with ultrasounds,” says Sanchez, now the startup’s chip design lead. “But, eventually, everyone from paramedics to nurses to doctors who have never used ultrasound will carry with them.”</p>
<p>A future aim is to sell directly to consumers, adds co-founder Jonathan Rothberg, a serial biotech entrepreneur. In the late 2000s, Rothberg moved DNA sequencing onto a semiconductor chip through his startup Ion Torrent, after pioneering the field of high-speed DNA sequencing at 454 Life Sciences — for which President Barack Obama awarded him the 2015 National Medal of Technology and Innovation.</p>
<p>Consider the consumerization of blood-pressure monitors and defibrillators, he says: “Those started in doctors’ offices and are now in people’s homes. In the next few years, we’ll work with the FDA, so anyone who wants a window into the human body can have it.”</p>
<p>In fact, the device has already proven valuable for consumer use: After joining the startup last year as chief medical officer, John Martin, a surgeon, was at a hospital testing the iQ. Having felt a lump in his throat for some time, he scanned his neck, which revealed a tumor that was then diagnosed as cancerous. He recently finished his first round of treatment.</p>
<p>“I actually became the first consumer patient,” Martin says. “That underscores how powerful having a device like this in hands of people themselves will be for the future of medical care. I’m the living evidence that … lives will be saved.”</p>
<p><strong>Ultrasound on a chip</strong></p>
<p>Ultrasound machines rely on transducers, small devices with embedded quartz crystals. Applying an electric current to the crystals makes them vibrate and produce sound waves travelling into a body. When returning echoes hit the crystals, they emit electrical currents that can be translated by electronics into an ultrasound image. The iQ’s low cost and accuracy is in part due to Sanchez’s work designing chips that function like the crystals but are manufactured at a drastically lower price point.</p>
<p>In 2010, Rothberg, inspired by his daughter’s struggle with kidney issues, was seeking ways to advance body imaging. At a conference, he heard a presentation from Max Tegmark, an MIT professor of physics who was working on connecting images from thousands of radio telescopes to measure energy from distant stars. The trick was developing a system — called a butterfly network — that split the data-processing between all antennae efficiently to capture quality images.</p>
<p>Rothberg approached Tegmark with a proposition. “I told Max that I’d love to use his ideas on imaging, and combine them with my recent success of DNA sequencing on semiconductors, to put an ultrasound machine on a chip,” Rothberg says. “I said I would start a company to do that … if he gave me smartest students from MIT.”</p>
<p>Enter Sanchez. After earning two bachelor’s degrees from MIT in electrical engineering and computer science and in mathematics, Sanchez was working in Tegmark’s lab. Rothberg and Sanchez met and founded Butterfly Network in 2011, and Sanchez then began the arduous task of integrating transducers directly onto chips. For help, the startup hired as chief technology officer Keith Fife '98, SM '99, who had helped design the DNA-sequencing chips for Ion Torrent.</p>
<p>Rothberg also brought on board MIT alumnus, Kailiang Chen, SM ’09, PhD ’14, who worked to enable the transmitting/receiving circuit to talk to the transducer. Jason Gavris '10 joined in Butterfly Network in 2016 to help develop the iQ's infrastructure — specifically to make it easy to control the device with a single thumb.</p>
<p>After several iterations, Sanchez, Fife, and Chen found a way to integrate stacks of capacitive micromachined ultrasound transducers — basically, metal plates suspended between two electrodes — directly on a chip. (These devices function like crystal transducers.) From this, they created chips with roughly 9,000 transducer channels that, combined with electronics, could send out and receive sound waves and turn those waves into 3-D ultrasound images. Today, the computation power of each chip is extraordinary, Sanchez says: “Essentially, it has almost half a trillion operations per second behind it to swallow data to get ultrasound in and image out in real time.”</p>
<p><strong>User-friendly and universal</strong></p>
<p>To make imaging more user-friendly, the device leverages artificial intelligence (AI) and augmented reality (AR). Typically, Sanchez says, it takes a lot of training to acquire a quality body image without much difficulty — but takes only minutes with iQ.</p>
<p>If a user has difficulty positioning the iQ, AI algorithms detect the probe’s location and recognize what the user is most likely trying to scan. AR symbols direct the user where to position the probe. “The user points the phone’s camera at the probe and they get a 3-D arrow telling them to move up or tilt it,” Sanchez says. “We’ve pulled people off the street and had them find a valid view of the heart in about a minute and a half.”</p>
<p>Another MIT alumnus, Alex Rothberg ’09, who pioneered the deep learning at Butterfly Network, is now developing the artificial intelligence at another of Rothberg’s startups.</p>
<p>The iQ is also the first universal ultrasound device that can image an entire body. Crystals in ultrasound devices resonate at one narrow frequency tailored to individual areas. A user will need one probe to capture, say, a patient’s veins and another to image the heart or kidney. “These pieces have narrow bandwidths tailored to each application,” Sanchez says. “But our device has a very broad bandwidth that can essentially become any other probe at any time.”</p>
<p>Currently, the iQ is selling only in the U.S. But Butterfly Network is in talks with nonprofits, such as the Bill and Melinda Gates Foundation, to bring it to the developing world. In many remote areas, clinicians don’t have access to ultrasound technologies that can be used to, say, detect fetal health issues that cause women to die in childbirth.</p>
<p>“This is a perfect solution,” Sanchez says. “Because it’s low cost, we can put in the hands of doctors in remote locations and instantly save thousands of lives. But, I know there will also be other areas in critical care and in emergency rooms around developed and developing worlds where people’s lives will be saved because of what we built. For me, that’s motivating.”</p>
Butterfly Network, a startup co-founded by MIT alumnus Nevada Sanchez ’10, SM ’11, has developed a low-cost, handheld scanner that generates clinical-quality ultrasounds on a smartphone. Ultrasounds are uploaded to the cloud, where any expert with permission can give second opinions or help analyze images.
Courtesy of Butterfly NetworkStartups, Innovation and Entrepreneurship (I&E), Alumni/ae, Physics, School of Science, Health, Health care, Medical devices, Mobile devices, iPhone, Android, smartphones, Imaging, Computer visionJ-WEL grant award announcement and call for proposals in education innovationhttp://news.mit.edu/2018/j-wel-grant-award-announcement-call-proposals-education-innovation-0201
Funding is available to MIT faculty to support educational innovations in pre-K-12, Higher Education, and Workplace Learning.Thu, 01 Feb 2018 16:00:00 -0500MIT Open Learninghttp://news.mit.edu/2018/j-wel-grant-award-announcement-call-proposals-education-innovation-0201<p>The Abdul Latif Jameel World Education Lab (<a href="http://jwel.mit.edu">J-WEL</a>) is a new MIT initiative that promotes excellence and transformation in global education through three collaboratives: pre-K-12 (pK-12), Higher Education, and Workplace Learning.</p>
<p>Hazel Sive, a professor of biology and the faculty director of Higher Education at J-WEL, recently announced recipients of fall 2017 J-WEL grants in Higher Education Innovation. They are:</p>
<ul>
<li>Associate Professor Azra Akšamija, Department of Architecture: Culturally Sensitive Design: <em>Art and Innovation in the Refugee Camp</em></li>
<li>Professor W. Craig Carter, Department of Materials Science and Engineering: <em>Improving Academic-Field-Specific Learning through Coding, Visualization, and Computational Thinking: The CodeSeal Project</em></li>
<li>Professor Christoph Paus, Department of Physics: <em>Fundamentals of Experimentation in the Physics Sciences using an Arduino</em></li>
</ul>
<p>J-WEL is announcing a call for proposals through spring 2018 J-WEL Education Innovation Grant Program. Grants should be focused on educational innovations for pK-12, Higher Education, and Workplace Learning — generating solutions that may have MIT relevance, as well as the potential for global impact.</p>
<p>For deadlines, the detailed call, proposal form, budget template, and access to additional related resources, please visit the J-WEL Education Innovation Grant Program pages:</p>
<ul>
<li><a href="http://bit.ly/JWEL_2018_pK12_CFP">pK-12</a>&nbsp;- due Feb. 23, 2018</li>
<li><a href="http://bit.ly/JWEL_2018_HE_CFP">Higher Education</a>&nbsp;- due March 9, 2018</li>
<li><a href="http://bit.ly/JWEL_2018_WPL_CFP">Workplace Learning</a>&nbsp;- due Feb. 23, 2018</li>
</ul>
<p>Please contact <a href="mailto:jwel-grants@mit.edu?subject=Grant%20Award%20Proposal">jwel-grants@mit.edu</a> with specific questions about the process or its requirements.</p>
International participants in J-WEL’s October 2017 inaugural J-WEL Week learn about educational innovations at MIT during the Learning Everywhere Project Showcase.Image: Ada RenAbdul Latif Jameel World Education Lab (J-WEL), Grants, Awards, honors and fellowships, Faculty, School of Architecture and Planning, School of Engineering, School of Science, Architecture, Materials Science and Engineering, Physics, DMSEModeling the universehttp://news.mit.edu/2018/modeling-universe-Vogelsberger-IllustrisTNG-0131
MIT&#039;s Mark Vogelsberger and an international astrophysics team have created a new model pointing to black holes’ role in galaxy formation.Wed, 31 Jan 2018 19:00:00 -0500Julia Keller | School of Sciencehttp://news.mit.edu/2018/modeling-universe-Vogelsberger-IllustrisTNG-0131<p>A supercomputer simulation of the universe has produced new insights into how black holes influence the distribution of dark matter, how heavy elements are produced and distributed throughout the cosmos, and where magnetic fields originate.&nbsp;</p>
<p>Astrophysicists from MIT, Harvard University, the Heidelberg Institute for Theoretical Studies, the Max-Planck Institutes for Astrophysics and for Astronomy, and the Center for Computational Astrophysics gained new insights into the formation and evolution of galaxies by developing and programming a new simulation model for the universe — “Illustris - The Next Generation” or <a href="http://www.tng-project.org/">IllustrisTNG</a>.&nbsp;</p>
<p>Mark Vogelsberger, an assistant professor of physics at MIT and the MIT Kavli Institute for Astrophysics and Space Research, has been working to develop, test, and analyze the new IllustrisTNG simulations. Along with postdocs Federico Marinacci and Paul Torrey, Vogelsberger has been using IllustrisTNG to study the observable signatures from large-scale magnetic fields that pervade the universe.&nbsp;</p>
<p>Vogelsberger used the IllustrisTNG model to show that the turbulent motions of hot, dilute gases drive small-scale magnetic dynamos that can exponentially amplify the magnetic fields in the cores of galaxies — and that the model accurately predicts the observed strength of these magnetic fields.</p>
<p>“The high resolution of IllustrisTNG combined with its sophisticated galaxy formation model allowed us to explore these questions of magnetic fields in more detail than with any previous cosmological simulation," says Vogelsberger, an author on the three papers reporting the new work, published today in the <em>Monthly Notices of the Royal Astronomical Society</em>.</p>
<p><strong>Modeling a (more) realistic universe&nbsp;</strong></p>
<p>The IllustrisTNG project is a successor model to the original <a href="http://www.illustris-project.org/" target="_blank">Illustris simulation</a> developed by this same research team but has been updated to include some of the physical processes that play crucial roles in the formation and evolution of galaxies.&nbsp;</p>
<p>Like Illustris, the project models a cube-shaped piece of the universe. This time, the project followed the formation of millions of galaxies in a representative region of the universe with nearly 1 billion light years on a side (up from 350 million light years on a side just four years ago). lllustrisTNG is the largest hydrodynamic simulation project to date for the emergence of cosmic structures, says Volker Springel, principal investigator of IllustrisTNG and a researcher at Heidelberg Institute for Theoretical Studies, Heidelberg University, and the Max-Planck Institute for Astrophysics.</p>
<p>The cosmic web of gas and stars predicted by IllustrisTNG produces galaxies quite similar to the shape and size of real galaxies. For the first time, hydrodynamical simulations could directly compute the detailed clustering pattern of galaxies in space. In comparison with observational data — including the newest large galaxy surveys such as the Sloan Digital Sky Survey — IllustrisTNG demonstrates a high degree of realism, says Springel.&nbsp;</p>
<p>In addition, the simulations predict how the cosmic web changes over time, in particular in relation to the underlying backbone of the dark matter cosmos. “It is particularly fascinating that we can accurately predict the influence of supermassive black holes on the distribution of matter out to large scales,” says Springel. “This is crucial for reliably interpreting forthcoming cosmological measurements.”&nbsp;</p>
<p><strong>Astrophysics via code and supercomputers</strong>&nbsp;</p>
<p>For the project, the researchers developed a particularly powerful version of their highly parallel moving-mesh code AREPO and used it on the "<a href="https://www.hlrs.de/systems/cray-xc40-hazel-hen/">Hazel-Hen</a>" machine at the Supercomputing Center in Stuttgart, Germany's fastest mainframe computer.</p>
<p>To compute one of the two main simulation runs, more than 24,000 processors were used over the course of more than two months.</p>
<p>“The new simulations produced more than 500 terabytes of simulation data,” says Springel. “Analyzing this huge mountain of data will keep us busy for years to come, and it promises many exciting new insights into different astrophysical processes."&nbsp;</p>
<p><strong>Supermassive black holes squelch star formation</strong></p>
<p>In another study, Dylan Nelson, researcher at the Max-Planck Institute for Astrophysics, was able to demonstrate the important impact of black holes on galaxies.</p>
<p>Star-forming galaxies shine brightly in the blue light of their young stars until a sudden evolutionary shift quenches the star formation, such that the galaxy becomes dominated by old, red stars, and joins a graveyard full of old and dead galaxies.&nbsp;</p>
<p>“The only physical entity capable of extinguishing the star formation in our large elliptical galaxies are the supermassive black holes at their centers,” explains Nelson. “The ultrafast outflows of these gravity traps reach velocities up to 10 percent of the speed of light and affect giant stellar systems that are billions of times larger than the comparably small black hole itself.“</p>
<p><strong>New findings for galaxy structure</strong></p>
<p>IllustrisTNG also improves researchers' understanding of the hierarchical structure formation of galaxies. Theorists argue that small galaxies should form first, and then merge into ever-larger objects, driven by the relentless pull of gravity. The numerous galaxy collisions literally tear some galaxies apart and scatter their stars onto wide orbits around the newly created large galaxies, which should give them a faint background glow of stellar light.</p>
<p>These predicted pale stellar halos are very difficult to observe due to their low surface brightness, but IllustrisTNG was able to simulate exactly what astronomers should be looking for.&nbsp;</p>
<p>“Our predictions can now be systematically checked by observers,” says Annalisa Pillepich, a researcher at Max-Planck Institute for Astronomy, who led a further Illustris-TNG study. “This yields a critical test for the theoretical model of hierarchical galaxy formation.”&nbsp;</p>
Rendering of the gas velocity in a thin slice of 100 kiloparsec thickness (in the viewing direction), centered on the second most massive galaxy cluster in the TNG100 calculation. Where the image is black, the gas is hardly moving, while white regions have velocities that exceed 1,000 kilometers per second. The image contrasts the gas motions in cosmic filaments against the fast chaotic motions triggered by the deep gravitational potential well and the supermassive black hole sitting at its center.Image courtesy of the IllustrisTNG collaborationSchool of Science, Astrophysics, Physics, Kavli Institute, Research, Black holes, Dark matter, space, Space, astronomy and planetary scienceNovel methods of synthesizing quantum dot materialshttp://news.mit.edu/2018/mit-researchers-optimizing-quantum-dot-materials-0124
MIT researchers are optimizing nanostructures for energy devices such as solar cells.
Wed, 24 Jan 2018 17:00:00 -0500Nancy W. Stauffer | MIT Energy Initiativehttp://news.mit.edu/2018/mit-researchers-optimizing-quantum-dot-materials-0124<p>For quantum dot (QD) materials to perform well in devices such as solar cells, the nanoscale crystals in them need to pack together tightly so that electrons can hop easily from one dot to the next and flow out as current. MIT researchers have now made QD films in which the dots vary by just one atom in diameter and are organized into solid lattices with unprecedented order. Subsequent processing pulls the QDs in the film closer together, further easing the electrons’ pathway. Tests using an ultrafast laser confirm that the energy levels of vacancies in adjacent QDs are so similar that hopping electrons don’t get stuck in low-energy dots along the way.</p>
<p>Taken together, the results suggest a new direction for ongoing efforts to develop these promising materials for high performance in electronic and optical devices.</p>
<p>In recent decades, much research attention has focused on electronic materials made of quantum dots, which are tiny crystals of semiconducting materials a few nanometers in diameter. After three decades of research, QDs are now being used in TV displays, where they emit bright light in vivid colors that can be fine-tuned by changing the sizes of the nanoparticles. But many opportunities remain for taking advantage of these remarkable materials.</p>
<p>“QDs are a really promising underlying materials technology for energy applications,” says&nbsp;William Tisdale, the ARCO Career Development Professor in Energy Studies and an associate professor of chemical engineering.</p>
<p>QD materials pique his interest for several reasons. QDs are easily synthesized in a solvent at low temperatures using standard procedures. The QD-bearing solvent can then be deposited on a surface — small or large, rigid or flexible — and as it dries, the QDs are left behind as a solid. Best of all, the electronic and optical properties of that solid can be controlled by tuning&nbsp;the QDs.</p>
<p>“With QDs, you have all these degrees of freedom,” says Tisdale. “You can change their composition, size, shape, and surface chemistry to fabricate a material that’s tailored for your application.”</p>
<p>The ability to adjust electron behavior to suit specific devices is of particular interest. For example, in solar photovoltaics (PVs), electrons should pick up energy from sunlight and then move rapidly through the material and out as current before they lose their excess energy. In light-emitting diodes (LEDs), high-energy “excited” electrons should relax on cue, emitting their extra energy as light.</p>
<p>With thermoelectric (TE) devices, QD materials could be a game-changer. When TE materials are hotter on one side than the other, they generate electricity. So TE devices could turn waste heat in car engines, industrial equipment, and other sources into power — without combustion or moving parts. The TE effect has been known for a century, but devices using TE materials have remained inefficient. The problem: While those materials conduct electricity well, they also conduct heat well, so the temperatures of the two ends of a device quickly equalize. In most materials, measures to decrease heat flow also decrease electron flow.</p>
<p>“With QDs, we can control those two properties separately,” says Tisdale. “So we can simultaneously engineer our material so it’s good at transferring electrical charge but bad at transporting heat.”</p>
<p><strong>Making good arrays</strong></p>
<p>One challenge in working with QDs has been to make particles that are all the same size and shape. During QD synthesis, quadrillions of nanocrystals are deposited onto a surface, where they self-assemble in an orderly fashion as they dry. If the individual QDs aren’t all exactly the same, they can’t pack together tightly, and electrons won’t move easily from one nanocrystal to the next.</p>
<p>Three years ago, a team in Tisdale’s lab led by Mark Weidman PhD ’16 demonstrated a way to reduce that structural disorder. In a series of experiments with lead-sulfide QDs, team members found that carefully selecting the ratio between the lead and sulfur in the starting materials would produce QDs of uniform size.</p>
<p>“As those nanocrystals dry, they self-assemble into a beautifully ordered arrangement we call a superlattice,” Tisdale says.</p>
<p>Scattering electron microscope images of those superlattices taken from several angles show lined-up, 5-nanometer-diameter nanocrystals throughout the samples and confirm the long-range ordering of the QDs.</p>
<p>For a closer examination of their materials, Weidman performed a series of X-ray scattering experiments at the National Synchrotron Light Source at Brookhaven National Laboratory. Data from those experiments showed both how the QDs are positioned relative to one another and how they’re oriented, that is, whether they’re all facing the same way. The results confirmed that QDs in the superlattices are well ordered and essentially all the same.</p>
<p>“On average, the difference in diameter between one nanocrystal and another was less than the size of one more atom added to the surface,” says Tisdale. “So these QDs have unprecedented monodispersity, and they exhibit structural behavior that we hadn’t seen previously because no one could make QDs this monodisperse.”</p>
<p><strong>Controlling electron hopping</strong></p>
<p>The researchers next focused on how to tailor their monodisperse QD materials for efficient transfer of electrical current. “In a PV or TE device made of QDs, the electrons need to be able to hop effortlessly from one dot to the next and then do that many thousands of times as they make their way to the metal electrode,” Tisdale explains.</p>
<p>One way to influence hopping is by controlling the spacing from one QD to the next. A single QD consists of a core of semiconducting material — in this work, lead sulfide — with chemically bound arms, or ligands, made of organic (carbon-containing) molecules radiating outward. The ligands play a critical role — without them, as the QDs form in solution, they’d stick together and drop out as a solid clump. Once the QD layer is dry, the ligands end up as solid spacers that determine how far apart the nanocrystals are.</p>
<p>A standard ligand material used in QD synthesis is oleic acid. Given the length of an oleic acid ligand, the QDs in the dry superlattice end up about 2.6 nanometers apart — and that’s a problem.</p>
<p>“That may sound like a small distance, but it’s not,” says Tisdale. “It’s way too big for a hopping electron to get across.”</p>
<p>Using shorter ligands in the starting solution would reduce that distance, but they wouldn’t keep the QDs from sticking together when they’re in solution. “So we needed to swap out the long oleic acid ligands in our solid materials for something shorter” after the film formed, Tisdale says.</p>
<p>To achieve that replacement, the researchers use a process called ligand exchange. First, they prepare a mixture of a shorter ligand and an organic solvent that will dissolve oleic acid but not the lead sulfide QDs. They then submerge the QD film in that mixture for 24 hours. During that time, the oleic acid ligands dissolve, and the new, shorter ligands take their place, pulling the QDs closer together. The solvent and oleic acid are then rinsed off.</p>
<p>Tests with various ligands confirmed their impact on interparticle spacing. Depending on the length of the selected ligand, the researchers could reduce that spacing from the original 2.6 nanometers with oleic acid all the way down to 0.4 nanometers. However, while the resulting films have beautifully ordered regions — perfect for fundamental studies — inserting the shorter ligands tends to generate cracks as the overall volume of the QD sample shrinks.</p>
<p><strong>Energetic alignment of nanocrystals</strong></p>
<p>One result of that work came as a surprise: Ligands known to yield high performance in lead-sulfide-based solar cells didn’t produce the shortest interparticle spacing in their tests.</p>
<p>“Reducing that spacing to get good conductivity is necessary,” says Tisdale. “But there may be other aspects of our QD material that we need to optimize to facilitate electron transfer.”</p>
<p>One possibility is a mismatch between the energy levels of the electrons in adjacent QDs. In any material, electrons exist at only two energy levels — a low ground state&nbsp;and a high excited state. If an electron in a QD film receives extra energy — say, from incoming sunlight — it can jump up to its excited state and move through the material until it finds a low-energy opening left behind by another traveling electron. It then drops down to its ground state, releasing its excess energy as heat or light.</p>
<p>In solid crystals, those two energy levels are a fixed characteristic of the material itself. But in QDs, they vary with particle size. Make a QD smaller and the energy level of its excited electrons increases. Again, variability in QD size can create problems. Once excited, a high-energy electron in a small QD will hop from dot to dot — until it comes to a large, low-energy QD.</p>
<p>“Excited electrons like going downhill more than they like going uphill, so they tend to hang out on the low-energy dots,” says Tisdale. “If there’s then a high-energy dot in the way, it takes them a long time to get past that bottleneck.”</p>
<p>So the greater mismatch between energy levels — called energetic disorder — the worse the electron mobility. To measure the impact of energetic disorder on electron flow in their samples, Rachel Gilmore PhD ’17 and her collaborators used a technique called pump-probe spectroscopy — as far as they know, the first time this method has been used to study electron hopping in QDs.</p>
<p>QDs in an excited state absorb light differently than do those in the ground state, so shining light through a material and taking an absorption spectrum provides a measure of the electronic states in it. But in QD materials, electron hopping events can occur within picoseconds — 10<sup>-12</sup>&nbsp;of a second — which is faster than any electrical detector can measure.</p>
<p>The researchers therefore set up a special experiment using an ultrafast laser, whose beam is made up of quick pulses occurring at 100,000 per second. Their setup subdivides the laser beam such that a single pulse is split into a pump&nbsp;pulse that excites a sample and — after a delay measured in femtoseconds (10<sup>-15</sup>&nbsp;seconds) — a corresponding probe&nbsp;pulse that measures the sample’s energy state after the delay. By gradually increasing the delay between the pump and probe pulses, they gather absorption spectra that show how much electron transfer has occurred and how quickly the excited electrons drop back to their ground state.</p>
<p>Using this technique, they measured electron energy in a QD sample with standard dot-to-dot variability and in one of the monodisperse samples. In the sample with standard variability, the excited electrons lose much of their excess energy within 3 nanoseconds. In the monodisperse sample, little energy is lost in the same time period — an indication that the energy levels of the QDs are all about the same.</p>
<p>By combining their spectroscopy results with computer simulations of the electron transport process, the researchers extracted electron hopping times ranging from 80 picoseconds for their smallest quantum dots to over 1 nanosecond for the largest ones. And they concluded that their QD materials are at the theoretical limit of how little energetic disorder is possible. Indeed, any difference in energy between neighboring QDs isn’t a problem. At room temperature, energy levels are always vibrating a bit, and those fluctuations are larger than the small differences from one QD to the next.</p>
<p>“So at some instant, random kicks in energy from the environment will cause the energy levels of the QDs to line up, and the electron will do a quick hop,” says Tisdale.</p>
<p><strong>The way forward</strong></p>
<p>With energetic disorder no longer a concern, Tisdale concludes that further progress in making commercially viable QD materials will require better ways of dealing with structural disorder. He and his team tested several methods of performing ligand exchange in solid samples, and none produced films with consistent QD size and spacing over large areas without cracks. As a result, he now believes that efforts to optimize that process “may not take us where we need to go.”</p>
<p>What’s needed instead is a way to put short ligands on the QDs when they’re in solution and then let them self-assemble into the desired structure.</p>
<p>“There are some emerging strategies for solution-phase ligand exchange,” he says. “If they’re successfully developed and combined with monodisperse QDs, we should be able to produce beautifully ordered, large-area structures well suited for devices such as solar cells, LEDs, and thermoelectric systems.”</p>
<p>QD synthesis and spectroscopy were supported by the US Department of Energy, Office of Basic Energy Sciences. Structural studies of QD solids were supported by the MIT Energy Initiative Seed Fund Program. Mark Weidman and Rachel Gilmore were partially supported by a National Science Foundation Graduate Research Fellowship. Measurements were performed at the Center for Functional Nanomaterials at Brookhaven National Laboratory, the Cornell High Energy Synchrotron Source, and the MRSEC Shared Experimental Facilities at MIT.&nbsp;</p>
<p>This article appeared&nbsp;in the&nbsp;<a href="http://energy.mit.edu/energy-futures/autumn-2017/">Autumn 2017&nbsp;issue </a>of <em>Energy Futures</em>, the magazine of the MIT Energy Initiative.</p>
Professor William Tisdale (left), Rachel Gilmore PhD '17, and their colleagues are developing novel methods of synthesizing quantum dot materials for use in solar cells, LEDs, and more. Testing confirms that their new techniques enable them to control the nanoscale structure of their materials — the key to high performance in energy devices.Photo: Stuart DarschMIT Energy Initiative, Research, Energy, Chemical engineering, School of Engineering, Chemistry, Physics, Nanoscience and nanotechnology, Solar, Renewable energy, SustainabilityTwelve School of Science faculty members appointed to named professorshipshttp://news.mit.edu/2018/mit-twelve-school-science-faculty-appointed-named-professorships-0119
Fri, 19 Jan 2018 15:00:00 -0500School of Sciencehttp://news.mit.edu/2018/mit-twelve-school-science-faculty-appointed-named-professorships-0119<p>The School of Science has appointed 12 faculty members to named professorships.</p>
<p>The new appointments are:</p>
<p><a href="https://biology.mit.edu/people/stephen_bell">Stephen Bell</a>, the Uncas (1923) and Helen Whitaker Professor in the Department of Biology: Bell is a leader in the field of DNA replication, specifically in the mechanisms controlling initiation of chromosome duplication in eukaryotic cells. Combining genetics, genomics, biochemistry, and single-molecule approaches, Bell has provided a mechanistic picture of the assembly of the bidirectional DNA replication machine at replication origins.</p>
<p><a href="https://eapsweb.mit.edu/people/twcronin">Timothy Cronin</a>, the Kerr-McGee Career Development Assistant Professor in the Department of Earth, Atmospheric and Planetary Sciences: Cronin is a climate physicist interested in problems relating to radiative‐convective equilibrium, atmospheric moist convection and clouds, and the physics of the coupled land‐atmosphere system.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/fakhri_nikta.html">Nikta Fakhri</a>, the Thomas D. and Virginia W. Cabot Assistant Professor in the Department of Physics: Combining approaches from physics, biology, and engineering, Fakhri seeks to understand the principles of active matter and aims to develop novel probes, such as single-walled carbon nanotubes, to map the organization and dynamics of nonequilibrium heterogeneous materials.</p>
<p><a href="http://chemistry.mit.edu/people/griffin-robert">Robert Griffin</a>, the Arthur Amos Noyes Professor in the Department of Chemistry: Griffin develops new magnetic resonance techniques to study molecular structure and dynamics and applies them to interesting chemical, biophysical, and physical problems such as the structure of large enzyme/inhibitor complexes, membrane proteins, and amyloid peptides and proteins.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/hewitt_jacqueline.html">Jacqueline Hewitt</a>, the Julius A. Stratton Professor in Electrical Engineering and Physics in the Department of Physics: Hewitt applies the techniques of radio astronomy, interferometry, and image processing to basic research in astrophysics and cosmology. Current topics of interest are observational signatures of the epoch of reionization and the detection of transient astronomical radio sources, as well as the development of new instrumentation and techniques for radio astronomy.</p>
<p><a href="http://math.mit.edu/directory/profile.php?pid=1464">William Minicozzi</a>, the Singer Professor of Mathematics in the Department of Mathematics: Minicozzi is a geometric analyst who, with colleague Tobias Colding, has resolved a number of major results in the field, among them: proof of a longstanding S.T. Yau conjecture on the function theory on Riemannian manifolds, a finite-time extinction condition of the Ricci flow, and recent work on the mean curvature flow. &nbsp;</p>
<p><a href="https://math.mit.edu/directory/profile.php?pid=1691">Aaron Pixton</a>, the Class of 1957 Career Development Assistant Professor in the Department of Mathematics: Pixton works on various topics in enumerative algebraic geometry, including the tautological ring of the moduli space of algebraic curves, moduli spaces of sheaves on 3-folds, and Gromov-Witten theory.&nbsp;</p>
<p><a href="http://chemistry.mit.edu/people/schlau-cohen-gabriela">Gabriela Schlau-Cohen</a>, the Thomas D. and Virginia W. Cabot Assistant Professor in the Department of Chemistry: Schlau-Cohen’s research employs single-molecule and ultrafast spectroscopies to explore the energetic and structural dynamics of biological systems. She develops new methodology to measure ultrafast dynamics on single proteins to study systems with both sub-nanosecond and second dynamics. In other research, she merges optical spectroscopy with model membrane systems to provide a novel probe of how biological processes extend beyond the nanometer scale of individual proteins.</p>
<p><a href="http://shaleklab.com/author/admin/">Alexander Shalek</a>, the Pfizer Inc.-Gerald Laubach Career Development Assistant Professor in the Department of Chemistry: Shalek studies how our individual cells work together to perform systems-level functions in both health and disease. Using the immune system as his primary model, Shalek leverages advances in nanotechnology and chemical biology to develop broadly applicable platforms for manipulating and profiling many interacting single cells in order to examine ensemble cellular behaviors from the bottom up.</p>
<p><a href="http://math.mit.edu/directory/profile.php?pid=243">Scott Sheffield</a>, the Leighton Family Professor in the Department of Mathematics: Sheffield is a probability theorist, working on geometrical questions that arise in such areas as statistical physics, game theory and metric spaces, as well as long-standing problems in percolation theory.</p>
<p><a href="https://eapsweb.mit.edu/people/solos">Susan Solomon</a>, the Lee and Geraldine Martin Professor in Environmental Studies in the Department of Earth, Atmospheric and Planetary Sciences: Solomon focuses on issues relating to both atmospheric climate chemistry and climate change, and is well-recognized for her insights in explaining the cause of the Antarctic ozone “hole” as well as her research on the irreversibility of global warming linked to anthropogenic carbon dioxide emissions and on the influence of the ozone hole on the climate of the southern hemisphere.</p>
<p><a href="https://biology.mit.edu/people/stefani_spranger">Stefani Spranger</a>, the Howard S. (1953) and Linda B. Stern Career Development Assistant Professor in the Department of Biology: Spranger studies the interactions between cancer and the immune system with the goal of improving existing immunotherapies or developing novel therapeutic approaches. Spranger seeks to understand how CD8 T cells, otherwise known as killer T cells, are excluded from the tumor microenvironment, with a focus on lung and pancreatic cancers.</p>
First row (l-r): Stephen Bell, Timothy Cronin, Nikta Fakhri, Robert Griffin. Second row (l-r): Jacqueline Hewitt, William Minicozzi, Aaron Pixton, Gabriela Schlau-Cohen. Third row (l-r): Alexander Shalek, Scott Sheffield, Susan Solomon, Stefani Spranger.Image courtesy of the School of ScienceSchool of Science, Biology, Chemistry, Earth and atmospheric sciences, Mathematics, Physics, Faculty, Awards, honors and fellowshipsTurning heat into electricityhttp://news.mit.edu/2018/topological-materials-turning-heat-electricity-0117
Study finds topological materials could boost the efficiency of thermoelectric devices.Tue, 16 Jan 2018 23:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2018/topological-materials-turning-heat-electricity-0117<p>What if you could run your air conditioner not on conventional electricity, but on the sun’s heat during a warm summer’s day? With advancements in thermoelectric technology, this sustainable solution might one day become a reality.</p>
<p>Thermoelectric devices are made from materials that can convert a temperature difference into electricity, without requiring any moving parts — a quality that makes thermoelectrics a potentially appealing source of electricity. The phenomenon is reversible: If electricity is applied to a thermoelectric device, it can produce a temperature difference. Today, thermoelectric devices are used for relatively low-power applications, such as powering small sensors along oil pipelines, backing up batteries on space probes, and cooling minifridges.</p>
<p>But scientists are hoping to design more powerful thermoelectric devices that will harvest heat — produced as a byproduct of industrial processes and combustion engines — and turn that otherwise wasted heat into electricity. However, the efficiency of thermoelectric devices, or the amount of energy they are able to produce, is currently limited.</p>
<p>Now researchers at MIT have discovered a way to increase that efficiency threefold, using “topological” materials, which have unique electronic properties. While past work has suggested that topological materials may serve as efficient thermoelectric systems, there has been little understanding as to how electrons in such topological materials would travel in response to temperature differences in order to produce a thermoelectric effect.</p>
<p>In a paper published this week in the <em>Proceedings of the National Academy of Sciences</em>, the MIT researchers identify the underlying property that makes certain topological materials a potentially more efficient thermoelectric material, compared to existing devices.</p>
<p>“We’ve found we can push the boundaries of this nanostructured material in a way that makes topological materials a good thermoelectric material, more so than conventional semiconductors like silicon,” says Te-Huan Liu, a postdoc in MIT’s Department of Mechanical Engineering. “In the end, this could be a clean-energy way to help us use a heat source to generate electricity, which will lessen our release of carbon dioxide.”</p>
<p>Liu is first author of the <em>PNAS </em>paper, which includes graduate students Jiawei Zhou, Zhiwei Ding, and Qichen Song; Mingda Li, assistant professor in the Department of Nuclear Science and Engineering; former graduate student Bolin Liao, now an assistant professor at the University of California at Santa Barbara; Liang Fu, the Biedenharn Associate Professor of Physics; and Gang Chen, the Soderberg Professor and head of the Department of Mechanical Engineering.</p>
<p><strong>A path freely traveled</strong></p>
<p>When a thermoelectric material is exposed to a temperature gradient — for example, one end is heated, while the other is cooled — electrons in that material start to flow from the hot end to the cold end, generating an electric current. The larger the temperature difference, the more electric current is produced, and the more power is generated. The amount of energy that can be generated depends on the particular transport properties of the electrons in a given material.</p>
<p>Scientists have observed that some topological materials can be made into efficient thermoelectric devices through nanostructuring, a technique scientists use to synthesize a material by patterning its features at the scale of nanometers. Scientists have thought that topological materials’ thermoelectric advantage comes from a reduced thermal conductivity in their nanostructures. But it is unclear how this enhancement in efficiency connects with the material’s inherent, topological properties.</p>
<p>To try and answer this question, Liu and his colleagues studied the thermoelectric performance of tin telluride, a topological material that is known to be a good thermoelectric material. The electrons in tin telluride also exhibit peculiar properties that mimic a class of topological materials known as Dirac materials.</p>
<p>The team aimed to understand the effect of nanostructuring on tin telluride’s thermoelectric performance, by simulating the way electrons travel through the material. To characterize electron transport, scientists often use a measurement called the “mean free path,” or the average distance an electron with a given energy would freely travel within a material before being scattered by various objects or defects in that material.</p>
<p>Nanostructured materials resemble a patchwork of tiny crystals, each with borders, known as grain boundaries, that separate one crystal from another. When electrons encounter these boundaries, they tend to scatter in various ways. Electrons with long mean free paths will scatter strongly, like bullets ricocheting off a wall, while electrons with shorter mean free paths are much less affected.</p>
<p>In their simulations, the researchers found that tin telluride’s electron characteristics have a significant impact on their mean free paths. They plotted tin telluride’s range of electron energies against the associated mean free paths, and found the resulting graph looked very different than those for most conventional semiconductors. Specifically, for tin telluride and possibly other topological materials, the results suggest that electrons with higher energy have a shorter mean free path, while lower-energy electrons usually possess a longer mean free path.</p>
<p>The team then looked at how these electron properties affect tin telluride’s thermoelectric performance, by essentially summing up the thermoelectric contributions from electrons with different energies and mean free paths. It turns out that the material’s ability to conduct electricity, or generate a flow of electrons, under a temperature gradient, is largely dependent on the electron energy.</p>
<p>Specifically, they found that lower-energy electrons tend to have a negative impact on the generation of a voltage difference, and therefore electric current. These low-energy electrons also have longer mean free paths, meaning they can be scattered by grain boundaries more intensively than higher-energy electrons.</p>
<p><strong>Sizing down</strong></p>
<p>Going one step further in their simulations, the team played with the size of tin telluride’s individual grains to see whether this had any effect on the flow of electrons under a temperature gradient. They found that when they decreased the diameter of an average grain to about 10 nanometers, bringing its boundaries closer together, they observed an increased contribution from higher-energy electrons.</p>
<p>That is, with smaller grain sizes, higher-energy electrons contribute much more to the material’s electrical conduction than lower-energy electrons, as they have shorter mean free paths and are less likely to scatter against grain boundaries. This results in a larger voltage difference that can be generated.</p>
<p>What’s more, the researchers found that decreasing tin telluride’s average grain size to about 10 nanometers produced three times the amount of electricity that the material would have produced with larger grains.</p>
<p>Liu says that while the results are based on simulations, researchers can achieve similar performance by synthesizing tin telluride and other topological materials, and adjusting their grain size using a nanostructuring technique. Other researchers have suggested that shrinking a material’s grain size might increase its thermoelectric performance, but Liu says they have mostly assumed that the ideal size would be much larger than 10 nanometers.</p>
<p>“In our simulations, we found we can shrink a topological material’s grain size much more than previously thought, and based on this concept, we can increase its efficiency,” Liu says.</p>
<p>Tin telluride is just one example of many topological materials that have yet to be explored. If researchers can determine the ideal grain size for each of these materials, Liu says topological materials may soon be a viable, more efficient alternative to producing clean energy.</p>
<p>“I think topological materials are very good for thermoelectric materials, and our results show this is a very promising material for future applications,” Liu says.</p>
<p>This research was supported in part by the Solid-State Solar Thermal Energy Conversion Center, an Energy Frontier Research Center of U.S. Department of Energy; and the Defense Advanced Research Projects Agency (DARPA).</p>
MIT researchers, looking for ways to turn heat into electricity, find efficient possibilities in certain topological materials.
Image: Christine Daniloff/MITEnergy, Materials science, Mechanical engineering, Physics, Research, School of Engineering, School of Science, Nuclear science and engineering, Department of Energy (DoE)New exotic phenomena seen in photonic crystals http://news.mit.edu/2018/new-exotic-phenomena-seen-photonic-crystals-0111
Researchers observe, for the first time, topological effects unique to an “open” system. Thu, 11 Jan 2018 14:00:00 -0500David L. Chandler | MIT News Officehttp://news.mit.edu/2018/new-exotic-phenomena-seen-photonic-crystals-0111<p>Topological effects, such as those found in crystals whose surfaces conduct electricity while their bulk does not, have been an exciting topic of physics research in recent years and were the subject of the 2016 Nobel Prize in physics. Now, a team of researchers at MIT and elsewhere has found novel topological phenomena in a different class of systems — open systems, where energy or material can enter or be emitted, as opposed to closed systems with no such exchange with the outside.</p>
<p>This could open up some new realms of basic physics research, the team says, and might ultimately lead to new kinds of lasers and other technologies.</p>
<p>The results are being reported this week in the journal <em>Science</em>, in a paper by recent MIT graduate Hengyun “Harry” Zhou, MIT visiting scholar Chao Peng (a professor at Peking University), MIT graduate student Yoseob Yoon, recent MIT graduates Bo Zhen and Chia Wei Hsu, MIT Professor Marin Soljačić, the Francis Wright Davis Professor of Physics John Joannopoulos, the Haslam and Dewey Professor of Chemistry Keith Nelson, and the Lawrence C. and Sarah W. Biedenharn Career Development Assistant Professor Liang Fu.</p>
<p>In most research in the field of topological physical effects, Soljačić says, so-called “open” systems — in physics terms, these are known as non-Hermitian systems — were not studied much in experimental work. The complexities involved in measuring or analyzing phenomena in which energy or matter can be added or lost through radiation generally make these systems more difficult to study and analyze in a controlled fashion.</p>
<p>But in this work, the team used a method that made these open systems accessible, and “we found interesting topological properties in these non-Hermitian systems,” Zhou says. In particular, they found two specific kinds of effects that are distinctive topological signatures of non-Hermitian systems. One of these is a kind of band feature they refer to as a bulk Fermi arc, and the other is an unusual kind of changing polarization, or orientation of light waves, emitted by the photonic crystal used for the study.</p>
<p>Photonic crystals are materials in which billions of very precisely shaped and oriented tiny holes are made, causing light to interact in unusual ways with the material. Such crystals have been actively studied for the exotic interactions they induce between light and matter, which hold the potential for new kinds of light-based computing systems or light-emitting devices. But while much of this research has been done using closed, Hermitian systems, most of the potential real-world applications involve open systems, so the new observations made by this team could open up whole new areas of research, the researchers say.</p>
<p>Fermi arcs, one of the unique phenomena the team found, defy the common intuition that energy contours are necessarily closed curves. They have been observed before in closed systems, but in those systems they always form on the two-dimensional surfaces of a three-dimensional system. In the new work, for the first time, the researchers found a Fermi arc that resides in the bulk of a system. This bulk Fermi arc connects two points in the emission directions, which are known as exceptional points — another characteristic of open topological systems.</p>
<p>The other phenomenon they observed consists of a field of light in which the polarization changes according to the emission direction, gradually forming a half-twist as one follows the direction along a loop and returns back to the starting point. “As you go around this crystal, the polarization of the light actually flips,” Zhou says.</p>
<p>This half-twist is analogous to a Möbius strip, he explains, in which a strip of paper is twisted a half-turn before connecting it to its other end, creating a band that has only one side. This Möbius-like twist in light polarization, Zhen says, could in theory lead to new ways of increasing the amount of data that could be sent through fiber-optic links.</p>
<p><br />
The new work is “mostly of scientific interest, rather than technological,” Soljačić says. Zhen adds that “now we have this very interesting technique to probe the properties of non-Hermitian systems.” But there is also a possibility that the work may ultimately lead to new devices, including new kinds of lasers or light-emitting devices, they say.</p>
<p>The new findings were made possible by <a href="http://news.mit.edu/2016/new-method-analyzing-photonic-crystals-1125">earlier research</a> by many of the same team members, in which they found a way to use light scattered from a photonic crystal to produce direct images that reveal the energy contours of the material, rather than having to calculate those contours indirectly.</p>
<p>“We had a hunch” that such half-twist behavior was possible and could be “quite interesting,” Soljačić says, but actually finding it required “quite a bit of searching to figure out, how do we make it happen?”</p>
<p>“Perhaps the most ingenious aspect of this work is that the authors use the fact that their system must necessarily lose photons, which is usually an obstacle and annoyance, to access new topological physics,” says Mikael Rechtsman, an assistant professor of physics at Pennsylvania State University who was not involved in this work. “Without the loss … this would have required highly complex 3-D fabrication methods that likely would not have been possible.” In other words, he says, the technique they developed “gave them access to 2-D physics that would have been conventionally thought impossible.”</p>
<p>The work was supported by the Army Research Office through the Institute for Soldier Nanotechnologies; S3TEC, an Energy Frontier Research Center funded by the U.S. Department of Energy; the U.S. Air Force; and the National Science Foundation.</p>
A drawing illustrates the unusual topological landscape around a pair of features known as exceptional points (red dots), showing the emergence of a Fermi arc (pink line at center), and exotic polarization contours that form a Mobius-strip-like texture (top and bottom strips).Courtesy of the researchersResearch, School of Science, Physics, Energy, Light, Photonics, Nanoscience and nanotechnology, Materials Research LaboratoryBose Grants for 2017 reward bold and unconventional research visions http://news.mit.edu/2017/bose-grants-reward-bold-and-unconventional-research-visions-1214
Six potentially paradigm-shifting research projects will make strides with funding from Professor Amar G. Bose Research Grants.Thu, 14 Dec 2017 17:30:01 -0500MIT Resource Developmenthttp://news.mit.edu/2017/bose-grants-reward-bold-and-unconventional-research-visions-1214<p>Since 2014, the Professor Amar G. Bose Research Grant has supported MIT faculty with innovative and potentially paradigm-shifting research ideas, and this year is no exception: With Bose funding, six research teams composed of nine MIT faculty members will pursue projects ranging from nanoengineering a light-emitting plant to developing solid-state atmospheric propulsion technology for aircraft. &nbsp;</p>
<p>Steven Barrett, John Hart, Dina Katabi, Timothy Swager, Michael Strano, Sheila Kennedy, Evelyn Wang, Justin Solomon, and Or Hen were recognized at a reception on Monday, Nov. 20, hosted by MIT President L. Rafael Reif and attended by past awardees. To celebrate the fifth anniversary of the Bose Grants, MIT also held a colloquium that included a panel discussion about the importance of philanthropic support for basic science research.</p>
<p>The grant program is named for the late Amar Bose ’51, SM ’52, ScD ’56, a longtime MIT faculty member and the founder of the Bose Corporation. This year’s reception also honored his son, Vanu Bose ’87, SM ’94, PhD ’99, who passed away last month. In his opening remarks, President Reif called Vanu the “heart and soul of the Bose program.” “For now, the best way to honor our friend is to appreciate together the wonderful gift that is the Bose research fellowship,” he said.</p>
<p>Vanu’s wife, Judith, spoke to the newest class of fellows about his boundless enthusiasm for the Bose Grants: “Vanu loved this moment. He loved it for the way that it so beautifully and perfectly celebrated the intellectual curiosity of his father, and of Bose Corporation. And he loved it because it was the moment he got to celebrate all of you.”</p>
<p>The grants support unconventional, ahead-of-the-curve, and often interdisciplinary research endeavors that are unlikely to be funded through traditional avenues, yet have the potential to lead to big breakthroughs. Bose Fellows, chosen this year from a pool of more than 100 applicants, receive up to $500,000 over three years of research. &nbsp;</p>
<p>“That is the promise of the Bose Fellowship, to help bold new ideas become realities, and I’m deeply grateful to the Bose family for making all of it possible,” Reif concluded.</p>
<p><strong>Reinventing propulsion for aircraft</strong></p>
<p>Is it possible to develop a propulsion system for drones and airplanes that involves no moving parts? That is the question that <a href="http://barrett.mit.edu/" target="_blank">Steven Barrett</a> will explore with his Bose Grant as he works on developing solid-state atmospheric propulsion technology.</p>
<p>“If you think about the history of aviation at a sort of fundamental level, the way in which aircraft are being propelled, the source of thrust, hasn't changed for over 100 years. It still needs a propeller or a turbine,” he explains.</p>
<p>Barrett’s research will employ a principle that involves ionizing air and accelerating the ionized air in an electrostatic field. As the accelerated ions collide with air molecules, they transfer momentum, creating a propulsive force.</p>
<p>“We have experiments that characterize the physics, efficiency, and effectiveness of creating this sort of propulsive force, and we've created simple prototypes as well,” Barrett says. “The next stage will be to try and make propulsion systems that are solid state that have the potential to be practically useful.”</p>
<p>For example, Barrett would like to integrate a solid-state propulsion system into the skin of an aircraft, eliminating the need for external engines or propellers. “The aircraft would pull itself through the air by ionizing air over its surface and then accelerating that air electrostatically,” Barrett explains.</p>
<p>Barrett is excited to use his Bose Grant to see how far forward he can push solid-state propulsion technology. “I think this project fits into the spirit of Bose, which is to do things that are clearly unconventional, high risk, and where you don't really know if it's going to work or not, but you think it's worth taking a risk,” he says.</p>
<p><strong>Building a more informative barcode</strong></p>
<p><a href="http://meche.mit.edu/people/faculty/ajhart@mit.edu" target="_blank">John Hart</a>, <a href="https://www.eecs.mit.edu/people/faculty/dina-katabi" target="_blank">Dina Katabi</a>, and <a href="http://chemistry.mit.edu/people/swager-timothy" target="_blank">Tim Swager</a> are developing a high-tech version of the barcodes used to identify everyday retail products. Their technology will combine a radio-frequency antenna with sensors to store and communicate detailed information about a product.</p>
<p>“Basically, you want to have a way of encoding what the product is, where was it born, when was it born, and what's its current state,” Swager explains. “And you'd like to have all of that [built]&nbsp;into something that's going to cost a penny or less.”</p>
<p>The researchers are working on building a radio-frequency antenna embedded with chemical sensors that change their electrical properties in response to chemical stimuli such as carbon dioxide or microbial activity. To keep costs down while scaling up, they will use fast, high- precision printing techniques.</p>
<p>“The goal is to come up with next generation types of resonant, radio-frequency circuits that are coupled into our chemistry, that then can be printed with great precision at high rates for all sorts of packaging applications,” Swager says.</p>
<p>The team hopes their next-generation barcode will help retailers, consumers, and distributors better understand product quality, and while they aren’t sure what the exact outcome will be, the researchers are confident that their cross-disciplinary efforts will produce something useful.</p>
<p>“This was a refreshingly interesting intersection of our areas of expertise, and it's a way to push the boundaries of each of our own research areas as the collective product,” Hart says, adding that Bose funding provides a unique chance for exploration. “The Bose Grant was an opportunity to ask the most open-ended question that we could, and to dream big,” he says.</p>
<p><strong>Seeking light from an unexpected source</strong></p>
<p>Engineer <a href="https://cheme.mit.edu/profile/michael-s-strano/" target="_blank">Michael Strano</a> and architect <a href="https://architecture.mit.edu/faculty/sheila-kennedy" target="_blank">Sheila Kennedy</a> are combining their expertise to develop the ultimate “green” energy technology: They are using nanotechnology to build plants that can provide lighting for buildings and cities.</p>
<p>“Plants are already well adapted for the outdoor environment. They self-repair, they already exist in the places where we would like lamps to function, they live and persist through weather events, they access their own water, and they do all of this autonomously.&nbsp;They're not on a power grid and produce and store their own fuel,” Strano explains. “In my laboratory, we've been asking the question of whether living plants could be the starting point of advanced technology.”</p>
<p>The team is developing a technique that uses four nanoparticles — tiny particles the size of the natural building blocks of a plant — to intercept a chemical pathway the plant uses to make adenosine triphosphate, or ATP, and divert some of this fuel to make the plant luminesce. “These plants are not going to be searchlights or floodlights, but we've calculated that they can have a level of brightness and duration that will serve many important applications,” Strano says.</p>
<p>“Really what we're talking about is a new form of living illumination infrastructure, which could involve many different species of wild-growing plants: single plants, plants aggregated, plants delivered and integrated into the built environment in new ways that are entirely different from the electrical grid paradigm,” Kennedy adds.</p>
<p>Realizing that it would be difficult to secure traditional funding for a project that combines nanotechnology, plant biology, architecture and urban design in such an unprecedented way, Strano and Kennedy looked to Bose. “The Bose is a unique and rare opportunity that MIT has for impactful thinking and the development of new ideas that are both completely logical and mind-blowing at the same time,” Kennedy says.</p>
<p><strong>Designing wires to transport heat </strong></p>
<p>With her Bose research grant, <a href="http://meche.mit.edu/people/faculty/enwang@mit.edu" target="_blank">Evelyn Wang</a> will attempt to design thermal wires that can efficiently transport heat long distances.</p>
<p>“We daily use electrical wires everywhere, we transfer electricity through the grid using these various cables around cities, and certainly that becomes a very powerful way for us to think about how we distribute electricity,” Wang explains. “However, it is very difficult to transfer thermal energy around the same types of distances, say on the order of hundreds of meters to kilometers.”</p>
<p>Wang is proposing a system that looks like an electrical wire, but takes advantage of the latent heat in liquid to vapor phase change. The wire will have an evaporator at one end that uses heat to vaporize liquid inside a pipe. The vapor will then travel to the other end of the wire, where a condenser will turn it back into a liquid, releasing heat in the process.</p>
<p>Wang is designing a new kind of evaporator that relies on surface tension forces, and she is building a condenser that uses mesh structures to facilitate the condensation process.</p>
<p>“It's kind of like a closed-loop system that looks almost like a solid material,” says Wang, “but there’s actually something passive that's working inside that allows us to be able to facilitate the effective thermal conductivity that you need to be able to now transfer across these length scales that we want.”</p>
<p>A Bose Grant has given Wang the flexibility to pursue what she calls “a little bit of a blue-sky project [that is] really highly exploratory.” “In some ways, the philosophy of what we want to do is quite different. It's something that I don’t think people will believe until they see that it actually works.”</p>
<p><strong>A better way of drawing voting districts</strong></p>
<p><a href="https://www.eecs.mit.edu/people/faculty/justin-solomon" target="_blank">Justin Solomon</a> is using a computer science approach to tackle gerrymandering, a centuries-old political issue that could easily affect the redrawing of voting districts after the 2020 census.</p>
<p>“There are a lot of cases where people engineer the vote that they receive by drawing the lines in a particular way. And it's a really critical issue for our democracy,” Solomon says. “This is one of the great problems at the intersection of mathematics, computation, and society.”</p>
<p>With funding from Bose, Solomon and his team, along with collaborators from the joint Tufts-MIT Metric Geometry and Gerrymandering Group, plan to develop computational tools that will help state lawmakers draw fair districts and help courts objectively assess whether existing districts have been drawn equitably.</p>
<p>One promising approach involves developing a computer program that can generate millions of different political redistricting plans for a given district. Lawmakers could then compare a newly drawn district to the computer-generated versions.</p>
<p>“If it turns out that among the millions and millions of plans that you generated, few if any share fairness properties with the plan drawn by a legislature, then you have a pretty strong argument that something went wrong,” Solomon says.</p>
<p>The team will also use their funding to turn what is currently a volunteer-based research effort into an academic discipline with full-time researchers.</p>
<p>Solomon is especially grateful for his Bose Grant because it is allowing his team to pursue research that could not be funded through traditional avenues. “I think especially in the mathematical and computational community, people are averse to funding what they perceive as politically risky, which is really a shame,” Solomon says. “I view this as a problem with our democracy regardless of what side of the aisle you're on.”</p>
<p><strong>A new approach to particle physics experiments</strong></p>
<p><a href="http://web.mit.edu/physics/people/faculty/hen_or.html" style="" target="_blank">Or Hen</a> is proposing a bold new approach to particle physics experiments: He will replace traditional long-term experiments involving thousands of researchers and large-scale accelerators with a simple tabletop beta-decay experiment called OLIVIA that can be repeated over and over again in the lab.</p>
<p>“Particle physics is one of the most fundamental aspects of science, where we try to understand what are the building blocks of the universe: the fundamental particles that we're all built of and their interactions,” Hen explains. “And now we're at a point where we know that there's new physics, in the sense that there are features of the universe that we can’t explain using the current particles and interactions that we know of, but so far we did not find any new ones in accelerators.”</p>
<p>Hen’s OLIVIA approach, which he calls “small and broad” involves analyzing nuclear beta decay of a radioactive isotope called lithium-8. To capture what happens during the beta decay process, he will use a new type of beta detector that is essentially a vessel full of gas. He will pump in gas containing lithium-8 nuclei, let it decay, and measure the resulting ionization, which is indicative of the decay process. &nbsp;</p>
<p>“The advantage of doing low-energy experiments is that I can actually do particle physics experiments in my lab at MIT, literally on a tabletop. This means looking for new physics in an indirect way, which also makes the search very broad,” Hen says. “By measuring the full kinematical distribution of the nuclear decay products, it's been shown that we can get great sensitivity to new physics.”</p>
<p>Hen’s innovative approach to particle physics experiments captures the essence of the Bose Grants. “Bose is an amazing opportunity that really allows me to add a new direction to my research,” Hen says. “Bose basically gives you the freedom to go out on a limb.”<br />
&nbsp;</p>
A Nov. 20 reception honored the MIT faculty receiving this year’s Professor Amar G. Bose Research Grants. The program is named for the late Amar Bose ’51, SM ’52, ScD ’56, a longtime MIT faculty member and the founder of the Bose Corporation. This year’s reception also honored his son, Vanu Bose ’87, SM ’94, PhD ’99, who passed away last month. In his opening remarks, President L. Rafael Reif called Vanu the “heart and soul of the Bose program.” “For now, the best way to honor our friend is to appreciate together the wonderful gift that is the Bose research fellowship,” he said.Image: John GilloolyAwards, honors and fellowships, Faculty, Grants, Funding, Aeronautical and astronautical engineering, Mechanical engineering, Electrical Engineering & Computer Science (eecs), Chemistry, Chemical engineering, Architecture, Physics, School of Engineering, School of Science, School of Architecture and Planning, Alumni/ae, Laboratory for Nuclear ScienceScientists observe supermassive black hole in infant universehttp://news.mit.edu/2017/scientists-observe-supermassive-black-hole-infant-universe-1206
Findings present a puzzle as to how such a huge object could have grown so quickly.Wed, 06 Dec 2017 13:00:00 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/scientists-observe-supermassive-black-hole-infant-universe-1206<p>A team of astronomers, including two from MIT, has detected the most distant supermassive black hole ever observed. The black hole sits in the center of an ultrabright quasar, the light of which was emitted just 690 million years after the Big Bang. That light has taken about 13 billion years to reach us — a span of time that is nearly equal to the age of the universe.</p>
<p>The black hole is measured to be about 800 million times as massive as our sun — a Goliath by modern-day standards and a relative anomaly in the early universe.</p>
<p>“This is the only object we have observed from this era,” says Robert Simcoe, the Francis L. Friedman Professor of Physics in MIT’s Kavli Institute for Astrophysics and Space Research. “It has an extremely high mass, and yet the universe is so young that this thing shouldn’t exist. The universe was just not old enough to make a black hole that big. It’s very puzzling.”</p>
<p>Adding to the black hole’s intrigue is the environment in which it formed: The scientists have deduced that the black hole took shape just as the universe was undergoing a fundamental shift, from an opaque environment dominated by neutral hydrogen to one in which the first stars started to blink on. As more stars and galaxies formed, they eventually generated enough radiation to flip hydrogen from neutral, a state in which hydrogen’s electrons are bound to their nucleus, to ionized, in which the electrons are set free to recombine at random. This shift from neutral to ionized hydrogen represented a fundamental change in the universe that has persisted to this day.</p>
<p>The team believes that the newly discovered black hole existed in an environment that was about half neutral, half ionized.</p>
<p>“What we have found is that the universe was about 50/50 — it’s a moment when the first galaxies emerged from their cocoons of neutral gas and started to shine their way out,” Simcoe says. “This is the most accurate measurement of that time, and a real indication of when the first stars turned on.”</p>
<p>Simcoe and postdoc Monica L. Turner are the MIT co-authors of a paper detailing the results, published today in the journal <em>Nature</em>. The other lead authors are from the Carnegie Institution for Science, in Pasadena, California.</p>
<p><strong>A shift, at high speed</strong></p>
<p>The black hole was detected by Eduardo Bañados, an astronomer at Carnegie, who found the object while combing through multiple all-sky surveys, or maps of the distant universe. Bañados was looking in particular for quasars — some of the brightest objects in the universe, that consist of a supermassive black hole surrounded by swirling, accreting disks of matter.</p>
<p>After identifying several objects of interest, Bañados focused in on them using an instrument known as FIRE (the Folded-port InfraRed Echellette), which was built by Simcoe and operates at the 6.5-meter-diameter Magellan telescopes in Chile. FIRE is a spectrometer that classifies objects based on their infrared spectra. The light from very distant, early cosmic objects shifts toward redder wavelengths on its journey across the universe, as the universe expands. Astronomers refer to this Doppler-like phenomenon as “redshift”; the more distant an object, the farther its light has shifted toward the red, or infrared end of the spectrum. The higher an object’s redshift, the further away it is, both in space and time.</p>
<p>Using FIRE, the team identified one of Bañados’ objects as a quasar with a redshift of 7.5, meaning the object was emitting light around 690 million years after the Big Bang. Based on the quasar’s redshift, the researchers calculated the mass of the black hole at its center and determined that it is around 800 million times the mass of the sun.</p>
<p>“Something is causing gas within the quasar to move around at very high speed, and the only phenomenon we know that achieves such speeds is orbit around a supermassive black hole,” Simcoe says.</p>
<p><strong>When the first stars turned on</strong></p>
<p>The newly identified quasar appears to inhabit a pivotal moment in the universe’s history. Immediately following the Big Bang, the universe resembled a cosmic soup of hot, extremely energetic particles. As the universe rapidly expanded, these particles cooled and coalesced into neutral hydrogen gas during an era that is sometimes referred to as the dark ages — a period bereft of any sources of light. Eventually, gravity condensed matter into the first stars and galaxies, which in turn produced light in the form of photons. As more stars turned on throughout the universe, their photons reacted with neutral hydrogen, ionizing the gas and setting off what’s known as the epoch of re-ionization.&nbsp;</p>
<p>Simcoe, Bañados, and their colleagues believe the newly discovered quasar existed during this fundamental transition, just at the time when the universe was undergoing a drastic shift in its most abundant element.</p>
<p>The researchers used FIRE to determine that a large fraction of the hydrogen surrounding the quasar is neutral. They extrapolated from that to estimate that the universe as a whole was likely about half neutral and half ionized at the time they observed the quasar. From this, they inferred that stars must have begun turning on during this time, 690 million years after the Big Bang.</p>
<p>“This adds to our understanding of our universe at large because we’ve identified that moment of time when the universe is in the middle of this very rapid transition from neutral to ionized,” Simcoe says. “We now have the most accurate measurements to date of when the first stars were turning on.”</p>
<p>There is one large mystery that remains to be solved: How did a black hole of such massive proportions form so early in the universe’s history? It’s thought that black holes grow by accreting, or absorbing mass from the surrounding environment. Extremely large black holes, such as the one identified by Simcoe and his colleagues, should form over periods much longer than 690 million years.</p>
<p>“If you start with a seed like a big star, and let it grow at the maximum possible rate, and start at the moment of the Big Bang, you could never make something with 800 million solar masses — it’s unrealistic,” Simcoe says. “So there must be another way that it formed. And how exactly that happens, nobody knows.”</p>
<p>This research was supported, in part, by the National Science Foundation (NSF), with support from construction of FIRE from NSF and from Curtis and Kathleen Marble.</p>
Artist’s conceptions of the most-distant supermassive black hole ever discovered, which is part of a quasar from just 690 million years after the Big Bang. It is surrounded by neutral hydrogen, indicating that it is from the period called the epoch of reionization, when the universe's first light sources turned on.
Image: Robin Dienel (Courtesy of the Carnegie Institution for Science)Astrophysics, Black holes, Kavli Institute, Physics, Research, School of Science, Space, astronomy and planetary science, National Science Foundation (NSF)Kolinda Grabar-Kitarović, president of Croatia, visits MIThttp://news.mit.edu/2017/kolinda-grabar-kitarovic-president-croatia-visits-mit-1205
State visit includes meeting with MIT president and award for MIT physicist Marin Soljačić.Tue, 05 Dec 2017 12:30:00 -0500Peter Dizikes | MIT News Officehttp://news.mit.edu/2017/kolinda-grabar-kitarovic-president-croatia-visits-mit-1205<p>Croatian president Kolinda Grabar-Kitarović visited MIT on Monday, discussing research and innovation policy, and bestowing two medals upon MIT Professor Marin Soljačić.</p>
<p>The state visit began in the office of MIT President L. Rafael Reif, who greeted Grabar-Kitarović and engaged with her in a discussion, partly about the need to have more women pursue careers in science, engineering, and mathematics. Reif also exchanged formal gifts with Grabar-Kitarović.</p>
<p>While in the MIT president’s office, Grabar-Kitarović presented Soljačić with two medals. One, for his special contributions to science, is the Order of the Croatian Morning Star, bearing the image of Ruder Bošković (a noted 18th-century physicist and astronomer from Dubrovnik). The other medal, the Order of the Croatian Interlace, is for contributions to Croatia’s development, reputation, and the welfare of its citizens.</p>
<p>Soljačić is a physicist and native of Zagreb, Croatia, whose work in photonics has produced a variety of new applications in fields ranging from solar energy to novel types of lasers.</p>
<p>Grabar-Kitarović, who was elected president of Croatia in 2015, called the visit to MIT “very inspiring” when she met later with a panel of Croatian students — mostly graduate students and postdocs — who are enrolled at MIT. Soljačić and Michael Sipser, the dean of the School of Science at MIT, were also part of the discussion forum.</p>
<p>Sipser presented an overview of basic research in science at MIT, from astronomy and physics to neuroscience and biology, and noted some of the recent fundamental advances in which MIT has played a role — such as the observation of gravitational waves, for which MIT physicist Rainer Weiss recently received the Nobel Prize.</p>
<p>“In many cases I’ve found that what attracts people to come into science are these fundamental discoveries,” Sipser said.</p>
<p>Soljačić, who runs the Photonics and Modern Electro-Magnetics Group at MIT, presented the forum with an overview of his research group’s advances — which apply to a wide range of topics and technologies, including more efficient solar cells, wireless power transfer, optical neural networks, and privacy for touch screens.</p>
<p>During the forum, Soljačić said he was “very honored” to have received the awards from Grabar-Kitarović and the government of Croatia; for her part, Grabar-Kitarović said it was “an honor for me too” to have presented them.</p>
<p>Grabar-Kitarović solicited input from the students at the panel about ways of encouraging Croatian students to stay in the country — or return to it, after a spell of study elsewhere — and to help add to the country’s intellectual ecosystem. She also noted that her country needed to address the “lack of opportunity” that some talented students can face when it comes to gaining a foothold in academic research.</p>
<p>“I hope with the help of the wonderful young people around the table, we will be able to help by bringing more science and technology [research] to Croatia,” Grabar-Kitarović said.</p>
<p>Grabar-Kitarović is the first female president in Croatia’s history. (The country declared independence from the former Yugoslavia in 1991.) Before becoming president, she served in a variety of governmental positions, including a term as Croatia’s ambassador to the U.S., from 2008 to 2011.</p>
<p>The Croatian delegation also included Pjer Simunovic, Croatia’s current ambassador to the U.S.</p>
<p>Soljačić is one of four Croatian-born faculty members at MIT. The others are Tanja Bosak, an associate professor in the Department of of Earth, Atmospheric and Planetary Sciences; Silvija Gradečak, a professor in the Department of Materials Science and Engineering; and economist Drazen Prelec, a professor in the MIT Sloan School of Management and the Department of Economics.</p>
The president of Croatia, Kolinda Grabar-Kitarović, visited MIT on Monday, Dec. 4. From left: MIT physicist Marin Soljačić; MIT President L. Rafael Reif; Croatian president Kolinda Grabar-Kitarović; and the dean of the MIT School of Science, Michael Sipser.
Image: Allegra BovermanPhysics, School of Science, Special events and guest speakers, International initiatives, International relations, President L. Rafael Reif, Faculty, EuropeJeremiah Johnson and Tracy Slatyer win 2017 School of Science Teaching Prizes http://news.mit.edu/2017/jeremiah-johnson-tracy-slatyer-win-school-of-science-teaching-prizes-1201
Faculty members in chemistry and physics honored for excellence in graduate and undergraduate teaching.Fri, 01 Dec 2017 17:40:02 -0500School of Sciencehttp://news.mit.edu/2017/jeremiah-johnson-tracy-slatyer-win-school-of-science-teaching-prizes-1201<p>The School of Science recently announced the winners of its 2017 Teaching Prizes for Graduate and Undergraduate Education. The prizes are awarded annually to School of Science faculty members who demonstrate excellence in teaching. Winners are chosen from nominations by their students or colleagues.</p>
<p><a href="http://chemistry.mit.edu/people/johnson-jeremiah" target="_blank">Jeremiah Johnson</a>, the Firmenich Career Development Associate Professor in the Department of Chemistry, was awarded the prize for undergraduate education for his role in 5.43 (Advanced Organic Chemistry). Nominators remarked on how his sincere enthusiasm and well-organized lectures and recitations made extremely challenging subject matter accessible and enjoyable.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/slatyer_tracy.html" target="_blank">Tracy Slatyer</a>, the Jerrold R. Zacharias Career Development Assistant Professor in the Department of Physics, was awarded the prize for graduate education for her course 8.323 (Relatavistic Quantum Field Theory I). While her nominators were impressed with her passion for and mastery of the subject, they especially appreciated that she made her students feel comfortable with asking many questions and that she carefully considered and answered each question.</p>
<p>The School of Science welcomes Teaching Prize nominations for its faculty during the spring semester each academic year. For more information please visit the&nbsp;<a href="http://science.mit.edu/policies/teaching-prizes-graduate-and-undergraduate-education" target="_blank">school's website</a>.</p>
Jeremiah Johnson (left) and Tracy Slatyer Awards, honors and fellowships, Faculty, Education, teaching, academics, Chemistry, Physics, School of ScienceScientists demonstrate one of largest quantum simulators yet, with 51 atomshttp://news.mit.edu/2017/scientists-demonstrate-one-largest-quantum-simulators-yet-51-atoms-1129
New technique manipulates atoms into antiferromagnetic state.Wed, 29 Nov 2017 13:00:00 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/scientists-demonstrate-one-largest-quantum-simulators-yet-51-atoms-1129<p>Physicists at MIT and Harvard University have demonstrated a new way to manipulate quantum bits of matter. In a paper published today in the journal <em>Nature</em>, they report using a system of finely tuned lasers to first trap and then tweak the interactions of 51 individual atoms, or quantum bits.</p>
<p>The team’s results represent one of the largest arrays of quantum bits, known as qubits, that scientists have been able to individually control. In the same issue of <em>Nature</em>, a team from the University of Maryland reports a similarly sized system using trapped ions as quantum bits.</p>
<p>In the MIT-Harvard approach, the researchers generated a chain of 51 atoms and programmed them to undergo a quantum phase transition, in which every other atom in the chain was excited. The pattern resembles a state of magnetism known as an antiferromagnet, in which the spin of every other atom or molecule is aligned.</p>
<p>The team describes the 51-atom array as not quite a generic quantum computer, which theoretically should be able to solve any computation problem posed to it, but a “quantum simulator” — a system of quantum bits that can be designed to simulate a specific problem or solve for a particular equation, much faster than the fastest classical computer.</p>
<p>For instance, the team can reconfigure the pattern of atoms to simulate and study new states of matter and quantum phenomena such as entanglement. The new quantum simulator could also be the basis for solving optimization problems such as the traveling salesman problem, in which a theoretical salesman must figure out the shortest path to take in order to visit a given list of cities. Slight variations of this problem appear in many other areas of research, such as DNA sequencing, moving an automated soldering tip to many soldering points, or routing packets of data through processing nodes.</p>
<p>“This problem is exponentially hard for a classical computer, meaning it could solve this for a certain number of cities, but if I wanted to add more cities, it would get much harder, very quickly,” says study co-author Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT. “For this kind of problem, you don’t need a quantum computer. A simulator is good enough to simulate the correct system. So we think these optimization algorithms are the most straightforward tasks to achieve.”</p>
<p>The work was performed in collaboration with Harvard professors Mikhail Lukin and Markus Greiner; MIT visiting scientist Sylvain Schwartz is also a co-author.</p>
<p><strong>Separate but interacting</strong></p>
<p>Quantum computers are largely theoretical devices that could potentially carry out immensely complicated computations in a fraction of the time that it would take for the world’s most powerful classical computer. They would do so through qubits — data processing units which, unlike the binary bits of classical computers, can be simultaneously in a position of 0 and 1. This quantum property of superposition allows a single qubit to carry out two separate streams of computation simultaneously. Adding additional qubits to a system can exponentially speed up a computer’s calculations.</p>
<p>But major roadblocks have prevented scientists from realizing a fully operational quantum computer. One such challenge: how to get qubits to interact with each other while not engaging with their surrounding environment.</p>
<p>“We know things turn classical very easily when they interact with the environment, so you need [qubits] to be super isolated,” says Vuletić, who is a member of the Research Laboratory of Electronics and the MIT-Harvard Center for Ultracold Atoms. “On the other hand, they need to strongly interact with another qubit.”</p>
<p>Some groups are building quantum systems with ions, or charged atoms, as qubits. They trap or isolate the ions from the rest of the environment using electric fields; &nbsp;once trapped, the ions strongly interact with each other. But many of these interactions are strongly repelling, like magnets of similar orientation, and are therefore difficult to control, particularly in systems with many ions.</p>
<p>Other researchers are experimenting with superconducting qubits — artificial atoms fabricated to behave in a quantum fashion. But Vuletić says such manufactured qubits have their disadvantages compared with those based on actual atoms.</p>
<p>“By definition, every atom is the same as every other atom of the same species,” Vuletić says. “But when you build them by hand, then you have fabrication influences, such as slightly different transition frequencies, couplings, et cetera.”</p>
<p><strong>Setting the trap</strong></p>
<p>Vuletić and his colleagues came up with a third approach to building a quantum system, using neutral atoms — atoms that hold no electrical charge — as qubits. Unlike ions, neutral atoms do not repel each other, and they have inherently identical properties, unlike fabricated superconducting qubits.</p>
<p>In previous work, the group <a href="http://news.mit.edu/2016/scientists-set-traps-atoms-single-particle-precision-1103">devised a way to trap individual atoms</a>, by using a laser beam to first cool a cloud of rubidium atoms to close to absolute zero temperatures, slowing their motion to a near standstill. They then employ a second laser, split into more than 100 beams, to trap and hold individual atoms in place. They are able to image the cloud to see which laser beams have trapped an atom, and can switch off certain beams to discard those traps without an atom. They then rearrange all the traps with atoms, to create an ordered, defect-free array of qubits.</p>
<p>With this technique, the researchers have been able to build a quantum chain of 51 atoms, all trapped at their ground state, or lowest energy level.</p>
<p>In their new paper, the team reports going a step further, to control the interactions of these 51 trapped atoms, a necessary step toward manipulating individual qubits. To do so, they temporarily turned off the laser frequencies that originally trapped the atoms, allowing the quantum system to naturally evolve.</p>
<p>They then exposed the evolving quantum system to a third laser beam to try and excite the atoms into what is known as a Rydberg state — a state in which one of an atom’s electrons is excited to a very high energy compared with the rest of the atom’s electrons. Finally, they turned the atom-trapping laser beams back on to detect the final states of the individual atoms.</p>
<p>“If all the atoms start in the ground state, it turns out when we try to put all the atoms in this excited state, the state that emerges is one where every second atom is excited,” Vuletić says. “So the atoms make a quantum phase transition to something similar to an antiferromagnet.”</p>
<p>The transition takes place only in every other atom due to the fact that atoms in Rydberg states interact very strongly with each other, and it would take much more energy to excite two neighboring atoms to Rydberg states than the laser can provide.</p>
<p>Vuletić says the researchers can change the interactions between atoms by changing the arrangement of trapped atoms, as well as the frequency or color of the atom-exciting laser beam. What’s more, the system may be easily expanded.</p>
<p>“We think we can scale it up to a few hundred,” Vuletić says. “If you want to use this system as a quantum computer, it becomes interesting on the order of 100 atoms, depending on what system you’re trying to simulate.”</p>
<p>For now, the researchers are planning to test the 51-atom system as a quantum simulator, specifically on path-planning optimization problems that can be solved using adiabatic quantum computing — a form of quantum computing first proposed by Edward Farhi, the Cecil and Ida Green Professor of Physics at MIT.</p>
<p>Adiabatic quantum computing proposes that the ground state of a quantum system describes the solution to the problem of interest. When that system can be evolved to produce the problem itself, the end state of the system can confirm the solution.</p>
<p>“You can start by preparing the system in a simple and known state of lowest energy, for instance all atoms in their ground states, then slowly deform it to represent the problem you want to solve, for instance, the traveling salesman problem,” Vuletić says. “It’s a slow change of some parameters in the system, which is exactly what we do in this experiment. So our system is geared toward these adiabatic quantum computing problems.”</p>
<p>This research was supported, in part, by the National Science Foundation, the Army Research Office, and the Air Force Office of Scientific Research.</p>
Physicists at MIT and Harvard University have demonstrated a new way to manipulate quantum bits of matter. The researchers report using a system of finely tuned lasers to first trap and then tweak the interactions of 51 individual atoms, or quantum bits.
Image: Christine Daniloff/MITAlgorithms, Physics, Quantum computing, Superconductors, Research, Research Laboratory of Electronics, School of ScienceCelebrating Milliehttp://news.mit.edu/2017/symposium-commemorates-pioneering-professor-mentor-mildred-dresselhaus-1129
Symposium commemorates the life and career of pioneering professor and beloved mentor Mildred Dresselhaus.Wed, 29 Nov 2017 10:30:18 -0500Maia Weinstock | MIT News Officehttp://news.mit.edu/2017/symposium-commemorates-pioneering-professor-mentor-mildred-dresselhaus-1129<p>They came from around the globe to commemorate a beloved mentor, collaborator, teacher, and world-renowned pioneer in solid-state physics and nanoscale engineering.</p>
<p>On Sunday, Nov. 26, the MIT community welcomed family, colleagues, friends, former students, and other associates of the late MIT Institute Professor Emerita Mildred “Millie” Dresselhaus to a daylong symposium celebrating her life.</p>
<p>Dresselhaus, an MIT faculty member for more than half a century, passed away at age 86 on Feb. 20, after a career in which she led in the development of numerous fields within materials science and engineering, particularly those related to the electronic structure of carbon. For her many accomplishments, Dresselhaus earned copious national and international accolades — including the National Medal of Science, the Kavli Prize, the Presidential Medal of Freedom, and worldwide recognition as the “Queen of Carbon.”</p>
<p>But Dresselhaus’ support of others, especially of women and underrepresented minorities; her service to local and national science and engineering societies; and her devotion to students and family were evidenced in equal measure at Sunday’s event, which drew a capacity crowd to Room 10-250 and to sessions in the lobbies of buildings 10 and 13.</p>
<p>“The first thing Millie taught me was the power of noticing,” MIT President L. Rafael Reif, who began at the Institute as a young professor in Dresselhaus’ home department of Electrical Engineering and Computer Science, said in his opening remarks. “Noticing patterns that others don’t see is essential to becoming and being a great scientist, and Millie surely had that gift.”</p>
<p>“But she used her amazing mind and heart to notice people, too,” Reif added. Dresselhaus, who as a student received guidance and encouragement from eminent physicists Rosalyn Yalow and Enrico Fermi, understood that “being noticed by the right person at the right time” could change the course of one’s career. And so, Reif explained, “Millie made part of her life’s work to notice others.”</p>
<p>Guests from various periods of Dresselhaus’ life filled the day with stories of her impact as a researcher and as a member of numerous communities, both at MIT and beyond.</p>
<p>In one session, colleagues from Mexico, Japan, Belgium, and elsewhere described Dresselhaus’ seminal contributions to the development of carbon science —&nbsp;from her work with graphite in the 1970s and 80s, to fullerines in the 1990s, to nanotubes in the 2000s, and back to graphite and two-dimensional graphene in the 2010s. Another session concentrated on her pioneering research developing nanomaterials in <a href="http://news.mit.edu/2010/explained-thermoelectricity-0427">thermoelectrics</a>, an area focused on turning temperature differences in materials into electricity.</p>
<p>One presentation slide depicted Dresselhaus’ extensive “family tree” of academic influence, which, based on publication citations, included some 900 collaborations over a half-century of research. A printed timeline, several dozen feet long, of life events and key scientific activities compiled by Dresselhaus’ granddaughter Shoshi Cooper gave attendees a visceral sense of the Institute Professor’s myriad travels, connections, and influences around the world.</p>
<p>But collaborators were often much more than just research partners; in many cases, they became lifelong friends — or family members. This began in the late 1950s with Dresselhaus’ partner in science and in life, husband and MIT staff researcher Gene Dresselhaus, who co-authored many papers and, as President Reif noted, four children. But it continued with her mentoring of dozens of graduate students and her connections to individuals across many realms of science research and education.</p>
<p>“What Millie and Gene gave me was deep encouragement,” said MIT colleague Jing Kong, a professor in the Department of Electrical Engineering and Computer Science. “I’m so thankful for what Millie has taught me and shown me. … I hope we can carry on [her] legacy.”</p>
<p>Dresselhaus’ service to society — whether as director of the U.S. Department of Energy’s Office of Science or as president of the American Physical Society (APS) and the American Association for the Advancement of Science, was also on display, as was her devotion to improving conditions for women and underrepresented minorities in science and engineering, both at MIT and elsewhere. Laurie McNeil, a former postdoc who is now a professor of physics at the University of North Carolina at Chapel Hill, described Dresselhaus’ leadership in developing for the APS a nationwide Climate for Women Site Visit Program, which represented a critical step in helping physics departments improve support for female students and faculty.</p>
<p>Closer to home, Institute Professor Sheila Widnall of the Department of Aeronautics and Astronautics, who spoke to attendees via prerecorded video, described some of the many positive changes Dresselhaus helped to bring about for women at MIT, who comprised just 4 percent of the student body when Dresselhaus first joined the Lincoln Laboratory in 1960. Later that decade, after becoming only the third woman (after Emily Wick and Widnall) to join MIT’s faculty in science or engineering, Dresselhaus felt a strong responsibility to advocate on behalf of female students and colleagues, and to be available for them in various supporting roles. “We all owe Millie a debt of gratitude,” Widnall said.</p>
<p>Looking forward, MIT Professor and Associate Dean for Innovation Vladimir Bulovic spoke of the many ways MIT hopes to extend Dresselhaus’ legacy in years to come. He noted that her personal papers would soon be donated to MIT’s Institute Archives for future generations to explore, and that her spirit would continue on in a series of Rising Stars workshops that bring young women in science and engineering to MIT for career development and networking. Bulovic was especially enthusiastic about Dresselhaus’ mark on MIT.nano, the state-of-the-art nanoscience and nanotechnology facility rising in the middle of campus. In a nod to her assertion that “My background is so improbable — that I’d be here from where I started,” Bulovic announced that a key courtyard between MIT.nano and the Infinite Corridor will be named “the Improbability Walk” in her honor.</p>
<p>The final session of the evening concluded with inspiration and song. As a lifelong violinist, Dresselhaus cherished orchestral and chamber music, and would play regularly in groups and in impromptu performances with family and friends. In tribute, loved ones including daughter Marianne and granddaughters Elizabeth and Clara capped the day’s presentations with pieces by Bach, Schumann, and Brahms.</p>
<p>MIT Corporation Life Member Shirley Ann Jackson ’68, PhD ’73, the president of Rensselaer Polytechnic Institute and a former student of Dresselhaus (who long held a joint appointment in the Department of Physics), also provided a warm tribute to her mentor via prerecorded video. “She was a woman of extraordinary focus, and always found opportunity within adversity and constraint,” Jackson said. “Her graceful adaptability and optimism offered me an important model as I encountered and stepped through my own unexpected windows of opportunity in industry, academia, and government. … Her unwillingness to allow struggling students to quit, and her efforts to break down institutional barriers for young women in science — including me — were a call to action for all of us who followed. … I am forever grateful to Millie Dresselhaus.”</p>
MIT President L. Rafael Reif welcomes family, colleagues, friends, former students, and other associates of the late MIT Institute Professor Mildred “Millie” Dresselhaus to a symposium celebrating her life and career.
Image: Maia WeinstockSpecial events and guest speakers, Faculty, Electrical Engineering & Computer Science (eecs), Physics, School of Engineering, School of Science, Materials Science and Engineering, Research Laboratory of Electronics, History of MIT, Women in STEM, Technology and society, MIT.nano, Carbon, Nanoscience and nanotechnology, Diversity and inclusionMaking others’ voices heard through education and journalismhttp://news.mit.edu/2017/student-profile-drew-bent-1128
Senior Drew Bent hopes to level the educational playing field of the future.Mon, 27 Nov 2017 23:59:59 -0500Fatima Husain | MIT News correspondenthttp://news.mit.edu/2017/student-profile-drew-bent-1128<p>Before senior Drew Bent began his undergraduate studies at MIT, he considered his interests in education to be “side projects.” He had worked at the educational platform Khan Academy and at Sony Ericsson while he was a high school student, employing what he had considered his main skill set since he was a child: programming.</p>
<p>“Basically, programming is all I did,” Bent says, “I used to be very much a technocrat.”</p>
<p>At MIT, Bent opted to double major in physics and electrical engineering and computer science. But he also dipped his toes in writing, as a journalist for MIT’s undergraduate newspaper, <em>The Tech</em>.</p>
<p>By the end of his first year, Bent had a revelation: “The stuff that I was doing that I was most passionate about — the work that could have the most positive impact — was actually the side projects,” Bent recalls. “It’s the MIT education that can actually help me and enable me to do really powerful things in these areas.”</p>
<p>Semesters later, Bent can further describe his vision.</p>
<p>“I’m very interested in leveling the playing field with education. I see education as a way to give everyone their own unique voice,” Bent says. “Journalism is making sure that voice is actually heard in a democratic process. Successful democracy requires an educated populace whose voices are all heard.”</p>
<p><strong>Newshound</strong></p>
<p>Since his freshman year, Bent has written over 35 articles for <em>The Tech</em>, covering campus news and research developments. Between his shorter news stories, Bent undertakes investigative journalism projects, some of which involve months of research.</p>
<p>“There are many aspects of journalism that are interesting, but the one that is most interesting to me is holding powerful actors accountable,” Bent says.</p>
<p>Bent’s reporting has spanned a wide variety of topics. His stories have included an investigation of an advertisement in <em>The Tech</em> that solicited an egg donor, a piece about the effects of a reorganization in MIT’s Information Services and Technology department, a profile of a student who was an Israeli military commander, and award-winning coverage of the trial of Dzhokhar Tsarnaev for his role in the Boston Marathon bombing. Other topics have included the closing of a fraternity, the discovery of gravitational waves, and other developments in student and residential life on campus.</p>
<p>“The [stories] that interest me are the ones that have someone whose voice wouldn’t have been heard otherwise and can actually lead to some change in policy,” Bent says, “Maybe [my writing] could start a conversation that wouldn’t have been there otherwise.”</p>
<p><strong>Education across America</strong></p>
<p>In the summer of 2015, Bent traveled with a group of MIT and Harvard University students to 11 towns across America by bicycle, through Spokes America, a student-run educational initiative founded in 2013 by Turner Bohlen ’14.</p>
<p>As part of the initiative, Bent helped plan and organize learning festivals in urban and rural towns, which featured workshops on computer science, mechanical engineering, and electrical engineering. Bent liked the out-of-the-classroom approach of the program, which is geared towards middle and high school students.</p>
<p>“[Spokes America] really lets the students take the initiative, giving them the environment to build rockets, computer programs, and robots,” Bent says, “Science and engineering don’t have to be learned from a textbook.”</p>
<p>During his travels from festival to festival, Bent saw how interested the attendees &nbsp;were in learning about engineering. Families who lived hours out of town would travel to festivals to partake in the Spokes America workshops.</p>
<p>“Everyone wants to bring everyone. Even parents want to go,” Bent says.</p>
<p>By using computer programming languages such as Scratch, which was developed by the MIT Media Lab’s Lifelong Kindergarten Group, participants were able to interact with engineering in a manner they hadn’t before.</p>
<p>Sometimes, Bent recalls, even children who hadn’t yet learned to read wanted to participate: “We weren’t going to say no to that.”</p>
<p><strong>Tutoring and beyond</strong></p>
<p>During the academic year, Bent regularly volunteers at the East End House, a Cambridge community center that holds educational programs for all ages.</p>
<p>Bent has worked at the East End House with 2nd- through 4th-graders since 2014. Students are bused after school to the community center, where they then work with Bent.</p>
<p>“First, they grab snacks, then you work with them for an hour on math and reading,” Bent says, “Then, you encourage them to go beyond.”</p>
<p>Sometimes, beyond isn’t much farther than the local playground.</p>
<p>“It goes beyond tutoring. You’re really becoming their buddy,” Bent says. What’s important to him is “the stuff that happens in the hours outside of the classroom.”</p>
<p>His volunteer work at the East End House is “usually the most rewarding part of the week, but also the most challenging part.”</p>
<p>“Students can tell if you’re not giving your best effort,” Bent says, “So you need to set a good example.”</p>
<p><strong>Building learning environments</strong></p>
<p>In November 2017, Bent had a conversation with one of his tutoring students about college.</p>
<p>“Somehow she thought that intelligence is what got people to universities like MIT,” Bent says, “It’s largely the hard work that gets you there. She was genuinely surprised that it was hard work, and not just some predetermined ability.”</p>
<p>Bent says that students “need to realize they’re capable of anything.”</p>
<p>Beyond MIT, he hopes to foster environments in which this kind of learning and realization is common. Bent envisions being what his journalism professor, Ethan Zuckerman, calls a “public interest technologist” and wants to use his technical and investigative background to reform education.&nbsp;</p>
<p>“The parts of education that I’m interested in are building learning environments —the more informal parts of education,” Bent says, “Whether it’s outside of school or bringing it into school.”</p>
<p>Bent believes his MIT education will be crucial in his pursuit.</p>
<p>“We often think of MIT as a place that develops technologies, but it also cultivates mindsets that are useful elsewhere in society,” Bent says. “The MIT education enables us to give back in more ways than we can imagine.”</p>
<p>Bent has also served as a member of the MIT OpenCourseWare Faculty Advisory Committee and has collaborated with Institute committees on developing an educational pilot program for students to do semester-long internships while taking online MIT courses. Along with senior Gabriel Ginorio, he has worked closely with Sanjay Sarma, MIT’s vice president for Open Learning. He has interned with the World Bank and spent this past summer working in the White House Office of Science and Technology Policy helping to draft national technology policy. He was also a high school physics teacher with the MISTI Global Teaching Labs in Italy.</p>
MIT senior Drew Bent regularly volunteers at the East End House, a Cambridge community center that holds educational programs for all ages.
Image: Ian MacLellanProfile, Students, Undergraduate, STEM education, Electrical Engineering & Computer Science (eecs), Physics, School of Engineering, School of Science, Technology and society, MISTI, online learning, education, Education, teaching, academics, Volunteering, outreach, public serviceA faster way to make Bose-Einstein condensateshttp://news.mit.edu/2017/faster-way-make-bose-einstein-condensates-1123
Method of laser cooling may speed up investigations into magnetism and superconductivity.Thu, 23 Nov 2017 13:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/faster-way-make-bose-einstein-condensates-1123<p>The world of an atom is one of random chaos and heat. At room temperatures, a cloud of atoms is a frenzied mess, with atoms zipping past each other and colliding, &nbsp;constantly changing their direction and speed.</p>
<p>Such random motions can be slowed, and even stopped entirely, by drastically cooling the atoms. At a hair above absolute zero, previously frenetic atoms morph into an almost zombie-like state, moving as one wave-like formation, in a quantum form of matter known as a Bose-Einstein condensate.</p>
<p>Since the first Bose-Einstein condensates were successfully produced in 1995 by researchers in Colorado and by Wolfgang Ketterle and colleagues at MIT, scientists have been observing their strange quantum properties in order to gain insight into a number of phenomena, including magnetism and superconductivity. But cooling atoms into condensates is slow and inefficient, and more than 99 percent of the atoms in the original cloud are lost in the process.</p>
<p>Now, MIT physicists have invented a new technique to cool atoms into condensates, which is faster than the conventional method and conserves a large fraction of the original atoms. The team used a new process of laser cooling to cool a cloud of rubidium atoms all the way from room temperature to 1 microkelvin, or less than one-millionth of a degree above absolute zero.</p>
<p>With this technique, the team was able to cool 2,000 atoms, and from that, generate a condensate of 1,400 atoms, conserving 70 percent of the original cloud. Their results are published today in the journal <em>Science</em>.</p>
<p>“People are trying to use Bose-Einstein condensates to understand magnetism and superconductivity, as well as using them to make gyroscopes and atomic clocks,” says Vladan Vuletić, the Lester Wolfe Professor of Physics at MIT. “Our technique could start to speed up all these inquiries.”</p>
<p>Vuletić is the senior author of the paper, which also includes first author and research assistant Jiazhong Hu, as well as Zachary Vendeiro, Valentin Crépel, Alban Urvoy, and Wenlan Chen.</p>
<p><strong>“A small fraction and a big drawback”</strong></p>
<p>Scientists have conventionally created Bose-Einstein condensates through a combination of laser cooling and evaporative cooling. The process generally begins by shining laser beams from several directions on a cloud of atoms. The photons in the beam act as tiny ping pong balls, bouncing off much larger, basketball-sized atoms, and slowing them down a little in each collision. The laser’s photons also act to compress the cloud of atoms, limiting their motion and cooling them in the process. But researchers have found there’s a limit to how much a laser can cool atoms: The more dense a cloud becomes, the less room there is for photons to scatter; instead they start to generate heat.</p>
<p>At this point in the process, scientists typically turn off the light and switch to evaporative cooling, which Vuletić describes as “like cooling a coffee cup — you just wait for the hottest atoms to escape.” But this is a slow process that ultimately removes more than 99 percent of the original atoms in order to retain the atoms that are cold enough to turn into Bose-Einstein condensates.</p>
<p>“In the end, you have to start with more than 1 million atoms to get a condensate consisting of only 10,000 atoms,” Vuletić says. “That’s a small fraction and a big drawback.”</p>
<p><strong>Tuning a twist</strong></p>
<p>Vuletić and his colleagues found a way to get around the initial limitations of laser cooling, to cool atoms into condensates using laser light from start to finish — a much faster, atom-conserving approach that he describes as a “longstanding dream” among physicists in the field.</p>
<p>“What we invented was a new twist on the method to make it work at high [atomic] densities,” Vuletić says.</p>
<p>The researchers employed conventional laser cooling techniques to cool a cloud of rubidium atoms down to just above the point at which atoms become so compressed that photons start to heat up the sample.</p>
<p>They then switched over to a method known as Raman cooling, in which they used a set of two laser beams to cool the atoms further. They tuned the first beam so that its photons, when absorbed by atoms, turned the atoms’ kinetic energy into magnetic energy. The atoms, in response, slowed down and cooled further, while still maintaining their original total energy.</p>
<p>The team then aimed a second laser at the much-compressed cloud, which was tuned in such a way that the photons, when absorbed by the slower atoms, removed the atoms’ total energy, cooling them even further.</p>
<p>“Ultimately the photons take away the energy of the system in a two-step process,” Vuletić says. “In one step, you remove kinetic energy, and in the second step, you remove the total energy and reduce the disorder, meaning you’ve cooled it.”</p>
<p>He explains that by removing the atoms’ kinetic energy, one is essentially doing away with their random motions and transitioning the atoms into more of a uniform, quantum behavior resembling Bose-Einstein condensates. These condensates can ultimately take form when the atoms have lost their total energy and cooled sufficiently to reside in their lowest quantum states.</p>
<p>To reach this point, the researchers found they had to go one step further to completely cool the atoms into condensates. To do so, they needed to tune the lasers away from atomic resonance, meaning that the light could more easily escape from the atoms without pushing them around and heating them.</p>
<p>“The atoms become almost transparent to the photons,” Vuletić says.</p>
<p>This means incoming photons are less likely to be absorbed by atoms, triggering vibrations and heat. Instead, every photon bounces off just one atom.</p>
<p>“Before, when a photon came in, it was scattered by, say, 10 atoms before it came out, so it made 10 atoms jitter,” Vuletić says. “If you tune the laser away from resonance, now the photon has a good chance of escaping before hitting any other atom. And it turns out by increasing the laser power, you can bring back the original cooling rate.”</p>
<p>The team found that with their laser cooling technique, they were able to cool rubidium atoms from 200 microkelvin to 1 microkelvin in just 0.1 seconds, in a process that is 100 times faster than the conventional method. What’s more, the group’s final sample of Bose-Einstein condensates contained 1,400 atoms, from an original cloud of 2,000, conserving a much larger fraction of condensed atoms compared with existing methods.</p>
<p>“When I was a graduate student, people had tried many different methods just using laser cooling, and it didn’t work, and people gave up. It was a longstanding dream to make this process simpler, faster, more robust,” Vuletić says. “So we’re pretty excited to try our approach on new species of atoms, and we think we can get it to get it to make 1,000-times-larger condensates in the future.”</p>
<p>This research was supported, in part, by the National Science Foundation, the Center for Ultracold Atoms, NASA, the Air Force Office of Science Research, and the Army Research Office.</p>
MIT physicists have invented a new technique to cool atoms into condensates, which is faster than the conventional method and conserves a large fraction of the original atoms.
Physics, Research, Atoms, Research Laboratory of Electronics, School of Science, National Science Foundation (NSF)Physicists design $100 handheld muon detectorhttp://news.mit.edu/2017/handheld-muon-detector-1121
Pocket-sized device detects charged particles in surrounding air. Mon, 20 Nov 2017 23:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/handheld-muon-detector-1121<p>At any given moment, the Earth’s atmosphere is showered with high-energy cosmic rays that have been blasted from supernovae and other astrophysical phenomena far beyond the Solar System. When cosmic rays collide with the Earth’s atmosphere, they decay into muons — charged particles that are slightly heavier than an electron.</p>
<p>Muons last only fractions of a second, and during their fleeting lifespan they can be found through every layer of the Earth’s atmosphere, circulating in the air around us and raining onto the surface at a rate similar to a light drizzle. A small fraction of muons can even penetrate the Earth’s surface and travel several kilometers through rock and ice.</p>
<p>Now physicists working in MIT's Laboratory for Nuclear Science have designed a pocket-sized cosmic ray muon detector to track these ghostly particles. The detector can be made with common electrical parts, and when turned on, it lights up and counts each time a muon passes through. The relatively simple device costs just $100 to build, making it the most affordable muon detector available today.</p>
<p>The researchers, led by Spencer Axani, a graduate student in MIT’s Department of Physics, have designed the detector with students in mind. They have started an outreach program called <a href="http://cosmicwatch.lns.mit.edu/">CosmicWatch</a>, with a <a href="http://cosmicwatch.lns.mit.edu/">website</a> that lists parts to purchase and detailed instructions on how to assemble, calibrate, and run the detector. The team estimates that an average high school student should spend about four hours building a detector for the first time, and just one hour building it a second time.</p>
<p>Once up and running, detectors can be carried around to measure muon rates in virtually any environment. The team has helped supply nearly 100 detectors to high school and college students, who have sent the instruments up in planes and weather balloons to measure muon rates at high altitudes. Students have also, as Axani has done, taken the detectors underground.</p>
<p>“You get funny looks when you take particle detectors into the subway, but we did that in Boston,” Axani says. “Since the muon rate will decrease the further down you go, we put the detectors in a subway station to measure how far underground we were.”</p>
<p>The researchers have published the first version of the detector design in the <em>American Journal of Physics</em>. Axani’s co-authors are MIT professor of physics Janet Conrad and junior Conor Kirby. Details regarding their latest version can be found on the CosmicWatch webpage.</p>
<p><strong>Treasure in trash</strong></p>
<p>Axani originally intended to build a small, handheld muon detector as a miniature add-on to IceCube, a huge particle detector encased in ice, deep underground at the South Pole. IceCube is designed to detect subatomic particles called neutrinos.</p>
<p>Scientists at the observatory proposed that a small muon detector might be inserted into PINGU (Precision IceCube Next Generation Upgrade), a proposed array that would increase the detector’s sensitivity to low-energy neutrinos. Small muon detectors, buried in such an array, would be able to tag the precise position of muons, enabling scientists to sift out those particles in their search for neutrinos.</p>
<p>Axani took on the task of designing a prototype muon detector for use in PINGU. Typical muon detectors consist of photomultiplying tubes lined with a scintillator, a material that emits light when struck by a charged particle. When a particle such as a muon bounces through the detector, the photomultiplying tube multiplies the current produced by the emitted light. In this way, even a single photon can make a current large enough that it can be measured. This is used to determine whether a muon or other particle has passed through the detector.</p>
<p>While most lab-scale muon detectors are made from large, bulky photomultipliers and even larger batteries to power them, Axani looked for ways to shrink the design.</p>
<p>After digging through discarded electronics equipment at MIT, he found the components he needed to build a much thinner device, requiring very little power.</p>
<p>He also designed simple electronics and software components to display the number of muons passing through the detector, making the detector a self-contained measurement and readout instrument.</p>
<p><strong>A project takes flight</strong></p>
<p>Since Axani first attempted to design a prototype, his project has morphed into more of an outreach effort, as he’s realized the components used to build the detector are relatively common, easily accessible, and simple to assemble — all ideal qualities for teaching students hands-on particle physics.</p>
<p>He, Conrad, and a colleague at the National Center for Nuclear Research in Poland, K. Frankiewicz, have assembled kits for students, which can be used to build individual handheld detectors about the size of a large cellphone. Each kit includes a piece of plastic scintillator, a SensL silicon photomultiplier, an Arduino Nano, a readout screen, a custom-designed printed circuit board, and a 3-D-printed casing, available in a rainbow of colors.</p>
<p>The team has supplied kits to students at the University of Warsaw in Poland, as well as the Missouri University of Science and Technology, where students have built an array of the detectors and sent them up in weather balloons to measure muons at high altitudes. Students have also taken the detectors onto planes to measure the different muon counts at various altitudes.</p>
<p>“At sea level, you might see one count every two seconds at sea level, but on a plane at cruising altitude, that rate increases by about a factor of 50 — a dramatic change,” Axani says. “From the measured rate you can back-calculate what the actual altitude of the plane was.”</p>
<p>A group at Boston University is also investigating the possibilities of placing the muon detectors in suborbital rockets, reaching altitudes of 100,000 feet.</p>
<p>“When you get up high enough, you get out of the muon production region of cosmic rays, and you can start seeing the turnover, where rates of muons increase at a certain altitude and then start decreasing beyond a certain altitude,” Conrad says.</p>
<p>Eventually, the researchers would like to apply their pocket detector as a means of muon tomography, a technique that uses the distribution of muons to create a three-dimensional image of the amount of material surrounding a detector. Scientists in the past have used muon tomography instruments, much like X-rays or CT scans, to uncover geological structures, the most famous of which was an effort in the 1960s to search for hidden chambers in the Pyramid of Chephren, in Giza.</p>
<p><strong>“</strong>That’s something I’d like to try out at some point, maybe to map out the office on the floor above me,” Axani says. “For now I like to take these detectors in my briefcase and measure the muon rate when I'm travelling.”</p>
<p>The researchers will continue to offer kits on the CosmicWatch website, along with instructions for how to assemble and apply them. They also hope to collect feedback from students and educators who have used the kits.</p>
<p>“This is a really neat example of how pretty esoteric physics can produce something which is directly useful,” Conrad says.</p>
<p>This research was funded, in part, by the National Science Foundation.</p>
Physicists at MIT have designed a pocket-sized cosmic ray muon detector to track these ghostly particles.
Courtesy of the researchersDepartment of Physics, Laboratory for Nuclear Science, Nuclear science and engineering, Physics, Research, School of Science, STEM education, K-12 educationA new window into electron behaviorhttp://news.mit.edu/2017/map-energy-momentum-electrons-beneath-material-surface-1116
Scientists invent technique to map energy and momentum of electrons beneath a material’s surface.Thu, 16 Nov 2017 15:30:00 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/map-energy-momentum-electrons-beneath-material-surface-1116<p>For the first time, physicists have developed a technique that can peer deep beneath the surface of a material to identify the energies and momenta of electrons there.</p>
<p>The energy and momentum of these electrons, known as a material’s “band structure,” are key properties that describe how electrons move through a material. Ultimately, the band structure determines a material’s electrical and optical properties.</p>
<p>The team, at MIT and Princeton University, has used the technique to probe a semiconducting sheet of gallium arsenide, and has mapped out the energy and momentum of electrons throughout the material. The results are published today in the journal <em>Science</em>.</p>
<p>By visualizing the band structure, not just at the surface but throughout a material, scientists may be able to identify better, faster semiconductor materials. They may also be able to observe the strange electron interactions that can give rise to superconductivity within certain exotic materials.</p>
<p>“Electrons are constantly zipping around in a material, and they have a certain momentum and energy,” says Raymond Ashoori, professor of physics at MIT and a co-author on the paper. “These are fundamental properties which can tell us what kind of electrical devices we can make. A lot of the important electronics in the world exist under the surface, in these systems that we haven’t been able to probe deeply until now. So we’re very excited — the possibilities here are pretty vast.”</p>
<p>Ashoori’s co-authors are postdoc Joonho Jang and graduate student Heun Mo Yoo, along with Loren Pfeffer, Ken West, and Kirk Baldwin, of Princeton University.</p>
<p><strong>Pictures beneath the surface</strong></p>
<p>To date, scientists have only been able to measure the energy and momentum of electrons at a material’s surface. To do so, they have used angle-resolved photoemission spectroscopy, or ARPES, a standard technique that employs light to excite electrons and make them jump out from a material’s surface. The ejected electrons are captured, and their energy and momentum are measured in a detector. Scientists can then use these measurements to calculate the energy and momentum of electrons within the rest of the material.</p>
<p>“[ARPES] is wonderful and has worked great for surfaces,” Ashoori says. “The problem is, there is no direct way of seeing these band structures within materials.”</p>
<p>In addition, ARPES cannot be used to visualize electron behavior in insulators — materials within which electric current does not flow freely. ARPES also does not work in a magnetic field, which can greatly alter electronic properties inside a material.</p>
<p>The technique developed by Ashoori’s team takes up where ARPES leaves off and enables scientists to observe electron energies and momenta beneath the surfaces of materials, including in insulators and under a magnetic field.</p>
<p>“These electronic systems by their nature exist underneath the surface, and we really want to understand them,” Ashoori says. “Now we are able to get these pictures which have never been created before.”</p>
<p><strong>Tunneling through</strong></p>
<p>The team’s technique is called momentum and energy resolved tunneling spectroscopy, or MERTS, and is based on quantum mechanical tunneling, a process by which electrons can traverse energetic barriers by simply appearing on the other side — a phenomenon that never occurs in the macroscopic, classical world which we inhabit. However, at the quantum scale of individual atoms and electrons, bizarre effects such as tunneling can occasionally take place.</p>
<p>“It would be like you’re on a bike in a valley, and if you can’t pedal, you’d just roll back and forth. You would never get over the hill to the next valley,” Ashoori says. “But with quantum mechanics, maybe once out of every few thousand or million times, you would just appear on the other side. That doesn’t happen classically.”</p>
<p>Ashoori and his colleagues employed tunneling to probe a two-dimensional sheet of gallium arsenide. Instead of shining light to release electrons out of a material, as scientists do with ARPES, the team decided to use tunneling to send electrons in.</p>
<p>The team set up a two-dimensional electron system known as a quantum well. The system consists of two layers of gallium arsenide, separated by a thin barrier made from another material, aluminum gallium arsenide. Ordinarily in such a system, electrons in gallium arsenide are repelled by aluminum gallium arsenide, and would not go through the barrier layer.</p>
<p>“However, in quantum mechanics, every once in a while, an electron just pops through,” Jang says.</p>
<p>The researchers applied electrical pulses to eject electrons from the first layer of gallium arsenide and into the second layer. Each time a packet of electrons tunneled through the barrier, the team was able to measure a current using remote electrodes. They also tuned the electrons’ momentum and energy by applying a magnetic field perpendicular to the tunneling direction. They reasoned that those electrons that were able to tunnel through to the second layer of gallium arsenide did so because their momenta and energies coincided with those of electronic states in that layer. In other words, the momentum and energy of the electrons tunneling into gallium arsenide were the same as those of the electrons residing within the material.</p>
<p>By tuning electron pulses and recording those electrons that went through to the other side, the researchers were able to map the energy and momentum of electrons within the material. Despite existing in a solid and being surrounded by atoms, these electrons can sometimes behave just like free electrons, albeit with an “effective mass” that may be different than the free electron mass. This is the case for electrons in gallium arsenide, and the resulting distribution has the shape of a parabola. Measurement of this parabola gives a direct measure of the electron’s effective mass in the material.</p>
<p><strong>Exotic, unseen phenomena</strong></p>
<p>The researchers used their technique to visualize electron behavior in gallium arsenide under various conditions. In several experimental runs, they observed “kinks” in the resulting parabola, which they interpreted as vibrations within the material.</p>
<p>“Gallium and arsenic atoms like to vibrate at certain frequencies or energies in this material,” Ashoori says. “When we have electrons at around those energies, they can excite those vibrations. And we could see that for the first time, in the little kinks that appeared in the spectrum.”</p>
<p>They also ran the experiments under a second, perpendicular magnetic field and were able to observe changes in electron behavior at given field strengths.</p>
<p>“In a perpendicular field, the parabolas or energies become discrete jumps, as a magnetic field makes electrons go around in circles inside this sheet,” Ashoori says.</p>
<p>“This has never been seen before.”</p>
<p>The researchers also found that, under certain magnetic field strengths, the ordinary parabola resembled two stacked donuts.</p>
<p>“It was really a shock to us,” Ashoori says.</p>
<p>They realized that the abnormal distribution was a result of electrons interacting with vibrating ions within the material.</p>
<p>“In certain conditions, we found we can make electrons and ions interact so strongly, with the same energy, that they look like some sort of composite particles: a particle plus a vibration together,” Jang says.</p>
<p>Further elaborating, Ashoori explains that “it’s like a plane, traveling along at a certain speed, then hitting the sonic barrier. Now there’s this composite thing of the plane and the sonic boom. And we can see this sort of sonic boom — we’re hitting this vibrational frequency, and there’s some jolt happening there.”</p>
<p>The team hopes to use its technique to explore even more exotic, unseen phenomena below the material surface.</p>
<p>“Electrons are predicted to do funny things like cluster into little bubbles or stripes,” Ashoori says. “These are things we hope to see with our tunneling technique. And I think we have the power to do that.”</p>
<p>This research was supported, in part, by the Gordon and Betty Moore Foundation&nbsp; and the BES program of the Office of Science of the U.S. Department of Energy.</p>
Scientists at MIT have found a way to visualize electron behavior beneath a material’s surface. The team’s technique is based on quantum mechanical tunneling, a process by which electrons can traverse energetic barriers by simply appearing on the other side. In this image, researchers show the measured tunneling spectra at various densities, with high measurements in red.
Courtesy of the researchersQuantum mechanics, Quantum Mechanics Energy, Physics, electronics, Research, School of Science, Semiconductors, Superconductors, Department of Energy (DoE)How to float your coffee creamerhttp://news.mit.edu/2017/droplets-levitate-liquid-surfaces-1115
Study explains how droplets can “levitate” on liquid surfaces.Tue, 14 Nov 2017 23:59:59 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/droplets-levitate-liquid-surfaces-1115<p>A drop or two of cold cream in hot coffee can go a long way toward improving one’s morning. But what if the two liquids didn’t mix?</p>
<p>MIT scientists have now explained why under certain conditions a droplet of liquid should not coalesce with the liquid surface below. If the droplet is very cold, and the bath sufficiently hot, then the droplet should “levitate” on the bath’s surface, as a result of the flows induced by the temperature difference.</p>
<p>The team’s results, published in the <em>Journal of Fluid Mechanics</em>, offer a detailed, mathematical understanding of drop coalescence, which can be observed in everday phenomena, from milk poured in coffee to raindrops skittering across puddles, and sprays created in surf zones.</p>
<div class="cms-placeholder-content-video"></div>
<p>The results may help researchers understand how biological or chemical substances are spread by rain or other sprays in nature. They could also serve as a guide for droplet-based designs, such as in microfluidic chips, in which droplets carrying various reagents can be designed to mix only in certain locations in a chip, at certain temperatures. With this new understanding, researchers could also engineer droplets to act as mechanical ball bearings in zero-gravity environments.</p>
<p>“Based on our new theory, engineers can determine what is the initial critical temperature difference they need to maintain two drops separately, and what is the maximum weight that a bearing constructed from these levitating drops would be able to sustain,” says Michela Geri, a graduate student in MIT’s Department of Mechanical Engineering and the study’s lead author. “If you have a fundamental understanding, you can start designing things the way you want them to work.”</p>
<p>Geri’s co-authors are Bavand Keshavarz, a lecturer in mechanical engineering, John Bush, professor of applied mathematics in MIT’s Department of Mathematics, and Gareth McKinley, the School of Engineering Professor of Teaching Innovation.</p>
<p><strong>An uplifting experiment</strong></p>
<p>The team’s results grew out of a question that Bush posed in his graduate course 18.357 (Interfacial Phenomena): Why should a temperature difference play a role in a droplet’s coalescence, or mixing?</p>
<p>Geri, who was taking the course at the time, took on the challenge, first by carrying out a series of experiments in McKinley’s lab.</p>
<p>She built a small box, about the size of an espresso cup, with acrylic walls and a metal floor, which she placed on a hot/cold plate. She filled the cube with a bath of silicone oil, and just above the surface of the bath she set a syringe through which she pumped droplets of silicone oil of the same viscosity. In each series of experiments, she set the temperature of the hot/cold plate, and measured the temperatures of the oil pumped through the syringe and at the surface of the bath.</p>
<p>Geri used a high-speed camera to record each droplet, at 2,000 frames per second, from the time it was released from the syringe to the time at which it mixed thoroughly with the bath. She performed this experiment using silicone oils with a range of viscosities, from water-like to 500 times thicker.</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/Mixing-Droplets-02.gif" style="width: 595px; height: 315px;" /></p>
<p><em><span style="font-size:10px;">Coalescence of a drop of cream into a bath of hot coffee. (Courtesy of the researchers)</span></em></p>
<p>She found that droplets appeared to levitate on a bath’s surface as the temperature gradient between the two fluids increased. She was able to levitate a droplet, delaying its coalescence, by as long as 10 seconds, by maintaining a temperature difference of up to 30 degrees Celsius, or 86 degrees Fahrenheit, comparable to the difference between a drop of cold milk on a bath of hot black coffee.</p>
<p>Geri plotted the data and observed that the droplet’s residence time on the bath’s surface seemed to depend on the initial temperature difference between the two fluids, raised to the power of two-thirds. She also noticed that there exists a critical temperature difference at which a droplet of a given viscosity will not mix but instead levitate on a liquid surface.</p>
<p>“We saw this relationship clearly in the lab and then tried to develop a theory in hopes of rationalizing that dependence,” Geri says.</p>
<p><img alt="" src="/sites/mit.edu.newsoffice/files/Mixing-Droplets-01.gif" style="width: 595px; height: 258px;" /></p>
<p><span style="font-size:10px;"><em>Visualization of recirculation vortices in the pending drop that is sitting on a warm bath. The temperature difference generates a recirculating flow that is visualized by shining a green laser light to the fluorescent particles that are added as passive tracers for sake of flow visualization. </em></span><em><span style="font-size:10px;">(Courtesy of the researchers)</span></em></p>
<p><strong>A cushion’s character</strong></p>
<p>The team first looked to characterize the layer of air separating the droplet from the bath. The researchers hypothesized that a temperature difference between the two fluids may influence this air cushion, which may in turn act to keep a droplet afloat.</p>
<p>To investigate this idea mathematically, the researchers performed a calculation, referred to in fluid mechanics as a lubrication analysis, in which they appropriately simplified the complex equations describing fluid motion, to describe the flow of air between the droplet and the bath.</p>
<p>Through these equations, they found that temperature differences between the fluid drop and the fluid bath create convection, or circulating currents in the intervening layer of air. The greater the temperature difference, the stronger the air currents, and the greater the pressure that pushes against the droplet’s weight, preventing it from sinking and making contact with the bath.&nbsp;</p>
<p>“We found the force coming from the droplet’s weight and the force coming from the recirculation of the air layer will balance at a point, and to get that balance, you need a minimum, or critical temperature difference, in order for the droplet to levitate,” Geri says.</p>
<p><strong>Inside a single drop</strong></p>
<p>Next, the team looked for a mathematical explanation for why they observed the 2:3 relationship between the amount of time a droplet levitates on a liquid surface and the initial temperature difference between the two fluids.</p>
<p>“For that, we had to think about how the temperature of the drop changes over time and approaches the temperature of the bath,” Geri says.</p>
<p>“With a temperature difference, you generate a flow inside the drop, drawing up heat from the bath, which circulates around until the droplet temperature is the same as the bath and you don’t levitate anymore,” Bush adds. “We were able to describe that process mathematically.”</p>
<p>To do so, the researchers adapted another set of equations, which describe the mixing of two fluids. They used the equations to model a warm parcel of liquid within the droplet that has been warmed by the bath below. They were able to characterize how that parcel of liquid mixed with the colder portions of the droplet, warming the entire droplet over time.</p>
<p>Through this modeling, they could observe how the temperature difference between fluids decreased over time, to the point at which a droplet stopped levitating and ultimately mixed with the rest of the bath.</p>
<p>“If you study that process mathematically, you can show the way in which temperature is changing in the droplet over time is exactly with this power law of 2/3 that we observed in our experiments,” Geri says.</p>
<p>Bush says that their results can be used to characterize the spread of certain chemical and biological agents that are transferred through raindrops and sprays.</p>
<p>“There are a lot of biological and chemical mixing events that involve droplet interactions, including in the surf zone, with waves breaking and small drops flying everywhere, and in hot tubs, with bubbles bursting and releasing droplets that skitter along the surface,” Bush says. “The rate at which these agents mix will depend on how long drops stay afloat before coalescing. Now we know that depends on temperature, and we can say exactly how.”</p>
<p>This research was supported, in part, by the National Science Foundation and MIT Energy Initiative through the Energy Fellowship Program.</p>
Visualization of vortices in a drop of silicone oil sitting on a warm bath. The temperature difference generates a recirculating flow that is visualized by shining a green laser light on fluorescent particles that are added as passive tracers within the drop.Courtesy of the researchersFluid dynamics, Mathematics, Mechanical engineering, Physics, Research, School of Engineering, School of ScienceBridging the divide with technologyhttp://news.mit.edu/2017mit-meet-bridging-middle-east-divide-with-technology-1114
Three from the Plasma Science and Fusion Center spend time with the Middle East Entrepreneurs of Tomorrow.Tue, 14 Nov 2017 12:10:00 -0500Paul Rivenberg | Plasma Science and Fusion Centerhttp://news.mit.edu/2017mit-meet-bridging-middle-east-divide-with-technology-1114<p>“Teach. Travel. Inspire.”</p>
<p>It was the fall of 2006 when first-year electrical engineering and computer science graduate student Ted Golfinopoulos read those words on a poster in&nbsp;the Infinite Corridor,&nbsp;inviting him to learn more about Middle East Education through Technology (MEET).&nbsp;The program, since renamed Middle East Entrepreneurs of Tomorrow, seeks to educate and empower promising Palestinian and Israeli high school students&nbsp;to foster relationships and mutual understanding using the study of science, technology, and entrepreneurship.</p>
<p>Eleven years after reading those three words, and now a research scientist at the MIT Plasma Science and Fusion Center (PSFC), Golfinopoulos&nbsp;has not only managed to devote time each year to the program, but to inspire new PSFC graduate students to apply. This past summer nuclear science and engineering grad student Adam Kuang and physics grad student Alex Tinguely joined him in what they say could be the beginning of an annual tradition.</p>
<p>“We were a little tentative a first to take time off, just because you are expected to be doing your research all the time,” Tinguely says. “But we spoke with our advisors who saw it as a good opportunity for us to grow as educators, work with a different population of students than we are used to, gain that cultural experience, and take a little break from research.”</p>
<p>Golfinopoulos recalls that he was compelled to apply after a summer traveling around Europe with a Turkish friend. Meeting up just as the 2006 Lebanon War was escalating, they were sensitive to the fact that their own friendship bridged historical conflicts and geopolitical issues between Greeks and Turks. “I think that the value and inspiration that can be drawn from people from different conflict groups meeting with one another was apparent to both of us at that time,” Golfinopoulos says.</p>
<p>Discovering MEET offered him a path to explore this further.</p>
<p>“The program purported to be helping excelling Palestinian and Israeli kids to know and trust each other and work together using science and information technology as a bridge,” he&nbsp;says. “Teaching is something I love to do. Computer science, a focus of the program, is an essential skill that I use everyday. This, I thought, is an opportunity for me to contribute to the solution of this problem.”</p>
<p>The competitive program, which is currently sponsored by the MIT International Science and Technology Initiatives (MISTI), a program of the MIT School of Humanities, Arts, and Social Sciences, generally accepts fewer than 10 percent of applicants, housing an equal number of Israeli and Palestinian, male and female students. Many travel for hours and cross cultural borders to be part of the three-year curriculum, which includes summer and winter intensives taught by MIT instructors. After completing a logical thinking test, a group dynamic test, and a personal interview, successful candidates receive full scholarships.</p>
<p>While the program nurtures connections and understanding between Israelis and Palestinians, it also has a significant impact on the MIT student instructors. Golfinopoulos acknowledges his own preconceptions about the Middle East were challenged. His early concerns that he would be judged for being American were quickly dispelled on a dusty road by a group of children who wanted nothing more than to have him find in his phrase book the words for “friendship” and “love.” He missed most of a scheduled luncheon talk playing word games with them.</p>
<p><strong>Experiencing the region</strong></p>
<p>Adam Kuang, traveling to Jerusalem for the first time this summer, says&nbsp;that the area was everything he had read about, and more.</p>
<p>“The reports, articles and books written about the region fail to capture how intricate and complex the situation is there,” he says. “Being on the ground made me all the more aware of just how interwoven the two communities are, especially in Jerusalem. They are so tightly woven together, yet you have so much tension because of it.”</p>
<p>Alex Tinguely admits he did not know much about the conflict before applying to teach in the program. He arrived with Kuang amid rising tensions, when in response to the killing of two police officers Israel had installed metal detectors at a site holy to both Jews and Muslims. The perception that Israel was purposely restricting Muslims from worshiping led to further violence. Tinguely was impressed by the way the residents carried on their lives.</p>
<p>“Even though a certain tension of the conflict was always present, I was surprised at how normal their lives were —&nbsp;having to come through checkpoints to come to school, having Israeli Defense Force (IDF) soldiers walk around with these huge automatic weapons … that’s very strange. Other than that everything was very normal. The kids were really excited to play sports with us, or they’d talk about popular celebrity news, and everyone had Snapchat. It was impressive to see how life can blossom in that area&nbsp;when you might think it would be too stifling. But they make it work.”</p>
<p>Golfinopoulos reports a similar experience. In the summer of 2014, violence escalated into a war between Hamas and the Israeli army. MIT had canceled travel to the region, citing safety concerns, but Golfinopoulos went on his own during a cease-fire. One evening, at midnight, the cease-fire ended.&nbsp;One minute later, air raid sirens announced the launch of an unguided missile toward the city, causing students and staff, Israelis and Palestinians, to walk together down the stairs toward a basement shelter —&nbsp;the only such occasion in MEET history.</p>
<p>“So what’s that like?” Golfinopoulos asks. “Giggling, nervous laughter, games, running around. Everyone was on nerves at some level. They wondered, ‘How are those from the other side going to treat me?’ But the overwhelming feeling of the students in that room was the excitement of ‘It’s midnight, and we are now up past curfew with all our friends, away from home.’”</p>
<p>But he adds, "It's easy to forget that as strong and brave as the students are, they are still deeply affected by the violence. They need that laughter and play to cope. &nbsp;And they also need to feel comfortable enough to show each other that they are upset, and vulnerable. &nbsp;We try to give them an outlet to express these feelings in a positive way,&nbsp;to say, 'This situation is not okay —&nbsp;this conflict is not normal —&nbsp;and it's up to us to chart a better path.' &nbsp;There’s much more to this region than war, and more than history —&nbsp;there is so much life."</p>
<p>Part of that teenage life inevitably involves social media, which, Kuang suggests, can spark conflict. “They’ve made these friends at MEET, and you get someone at home that puts something up on Facebook derogative of the other side.&nbsp;You like it,&nbsp;all your friends on the other side see that you liked it — it gets messy then.”</p>
<p>Golfinopoulos argues that while their youth may limit their perspective, it also allows the students to be more open.</p>
<p>“When they are young their humanity is always their louder voice. These students have heard not once, but many times, the narratives of their peers on the other side. And when they hear those stories they are hearing them from friends and people they care about. It’s not something they can ignore,” he&nbsp;says. “The powerful part of MEET is that it forces people to constantly reconcile being true to the communities they come from while recognizing the deep bonds and friendships they have with people who otherwise would be labeled their enemy.”&nbsp;</p>
<p><strong>Continuing bonds</strong></p>
<p>Bonds of friendship and support form as well between students and staff. One of Golfinopoulos’s former students is now a computer science professional and instructor at MEET.</p>
<p>“I have pictures of him as a student with cake on his face, and now he’s my colleague teaching alongside me,” he&nbsp;says. “He has started up a twin program for computer science education in the West Bank.”</p>
<p>Tinguely and Kuang still communicate with some of the students they taught this summer. Kuang is encouraged that many students have ended up coming to MIT because of this program.</p>
<p>“I can see the benefit of MEET because you open doors for people —&nbsp;doors in their minds that they might have closed off. And it has worked,” he&nbsp;says. “A lot of students have come to MIT because of the program. They have met MIT individuals,&nbsp;they have been encouraged to apply, and they get in. It is possible. You just have to keep working at it.”</p>
<p>Kuang and Tinguely both wish to stay involved with the program, but with the demands of a PhD fusion research program to address, they are not sure if yearly sojourns to Jerusalem will still be possible. Although his class focused on intro to Python, Tinguely did manage to use his PSFC expertise by providing seminars on the topic of fusion.</p>
<p>He says his teaching experience was a revelation.</p>
<p>“It gave me a lot of respect for teachers of all kinds, but in particular middle school to high school,” he&nbsp;says. “It was exhausting teaching for 6 to 7 hours a day, having to teach things over and over, explain things in different ways. We did that five and a half days a week, and I feel that is kind of what a high school teacher does. We did it for three weeks — they do it for the whole year.”</p>
<p>Golfinopoulos was thrilled to work in Jerusalem with his MIT colleagues, who typically support educational outreach with him at the PSFC. He believes&nbsp;that the MEET program provided them with leadership roles that they would not have as junior members of a research team back in Cambridge. “The influence they had on their students was palpable,” he notes, smiling. “There are now dozens of Israeli and Palestinians who want to pursue careers in science.”</p>
<p>Though optimistic, Golfinopoulos acknowledges the discouragement some of his students and colleagues experience from the conflict in the region. He describes meeting with an alumnus from his first year of teaching, an open-minded Israeli student on&nbsp;break from his military service.</p>
<p>“It was clear to me that he had lost hope. He felt like, as they say, ‘What’s the point? No matter what we do we can’t kick this thing.’&nbsp; That was hard to hear,” he&nbsp;says. “Despite that, 68 brand new kids came to MEET that year, defying not only the war but also people in their communities that exerted pressure on them not to attend and meet people from across the divide. And they met anyway.</p>
<p>“What gives me hope is their continued willingness to meet, and their belief in the value of doing this. Hope is a nice thing because you can lose it, and then you can find it again.”</p>
Left to right: MEET facilitators Ted Golfinopoulos, a PSFC research scientist, and graduate students Adam Kuang and Alex Tinguely spent time in Israel as part of program that provides a safe place for Israeli and Palestinian high school students to become colleagues in the study of science, technology, and entrepreneurship.Photo: Paul Rivenberg/PSFCGraduate, postdoctoral, International initiatives, MISTI, Volunteering, outreach, public service, Students, Classes and programs, SHASS, Plasma Science and Fusion Center, School of Engineering, Middle East, Electrical Engineering & Computer Science (eecs), Physics, School of Science, Nuclear science and engineering, StaffJesse Thaler: Seeking the fundamental nature of matter http://news.mit.edu/2017/faculty-profile-jesse-thaler-1107
Theorist explores particle physics at the boundary of “messy and elegant.” Tue, 07 Nov 2017 00:00:00 -0500Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/faculty-profile-jesse-thaler-1107<p>Jesse Thaler was a high school student in 1995, when a pivotal discovery in science turned his life’s path toward particle physics.</p>
<p>That year, physicists at the Fermi National Accelerator Laboratory confirmed that its Tevatron particle accelerator had detected, for the first time, a subatomic particle known as the top quark. This particle had been a missing piece in the Standard Model of particle physics — a theory that describes all the known elementary particles and several major, fundamental forces governing the universe.&nbsp;</p>
<p>“I remember my physics teacher had a big poster of the Standard Model on the wall, with a question mark next to the top quark,” says Thaler, who recently was granted tenure as an associate professor in MIT’s Department of Physics. “When it was discovered, I remember him writing down the mass of that top quark where there used to be a question mark. I thought discoveries must happen all the time. Little did I know that particle physics is a decades-long, even centuries-long, endeavor to try to understand the fundamental nature of matter, and that I would eventually become a part of that.”</p>
<p>Thaler, a member of MIT’s Center for Theoretical Physics and the Laboratory for Nuclear Science, is a self-described “pencil and paper, chalk and chalkboard” theorist, and works to derive theoretical insights to characterize the behavior of subatomic particles, and the fundamental forces that give structure to the universe.</p>
<p>He’s applying his theories to describe in greater detail the particles that are already known to the Standard Model, as well as predict the behavior of those beyond the Standard Model, which scientific theory cannot quite yet describe — namely, dark matter, which is thought to make up more than a quarter of the total mass-energy of the universe but has yet to be directly detected.</p>
<p>Thaler is collaborating with experimental physicists on projects ranging from small tabletop detectors to massive collaborations such as the Large Hadron Collider, and applying his theoretical insights to interpret data from current experiments and guide the design of future experiments.</p>
<p>“My research is always a balance between exploring what could, but might not, be there, and what must be there,” Thaler says. “Some would say everything should be beautiful and elegant and mathematical, and others would say the world is messy; you just have to study it. But at this boundary, it’s true some things are messy, and others are elegant, and living at that boundary is where I feel most comfortable.”</p>
<p><strong>“Subtleties at play”</strong></p>
<p>Thaler grew up in York, Maine, where his mother worked as a high school guidance counselor, and his father practiced family medicine. For high school, he attended Phillips Exeter Academy, where he quickly learned to think his way through tricky mathematical problems on his own.</p>
<p>“There wasn’t a textbook,” Thaler recalls. “You showed up the first day, they gave you a relatively thin stack of problems, and you went to class and had discussions but basically had to teach yourself. It was a very humanities-minded way of thinking of mathematics, which could also apply to physics.”</p>
<p>Thaler went on to Brown University, where he pursued a degree in math and physics, doing research into the formation of black holes, while also taking courses in the humanities, from Japanese theatre, to the role of women in Islamic society, to race relations in Brazilian history.</p>
<p>“Those classes helped me see that there is nuance, even in cases where you think things might be clear-cut,” Thaler says. “In physics, there are similar types of subtleties at play, where you can take different views on the same problem, and the answer comes from the full synthesis of those views. I try to take that approach in the physics research I do.”</p>
<p>To blow off some academic steam, Thaler picked up the electric bass as part of an eight-piece ’70s funk band, and put in late-night hours at the college radio station, playing jazz records under the pseudonym Lester, after legendary jazz saxophonist Lester Young. &nbsp;</p>
<p>“I would spin vinyl from 2 to 5:30 a.m. and then would have my 9 a.m. quantum mechanics class,” Thaler fondly recalls. “It was rough.”</p>
<p><strong>Flexible physics</strong></p>
<p>From Brown, he went on to graduate school at Harvard University, with the intention of studying string theory, which at the time was thought to uniquely explain the synthesis of gravity and quantum mechanics, in one unifying theory.</p>
<p>“Now I know that to be not quite the right story,” Thaler says. “The modern view of string theory is not that there’s one theory of everything, but many different theories that come out of string theory, and it’s a challenge to figure out which one of those corresponds to our universe, if any. So there’s not inevitability built in.”</p>
<p>During his second-semester quantum field theory course, Thaler’s professor, who would become his thesis advisor, helped him redirect his focus toward another theory, not of everything, but of almost everything: the Standard Model of particle physics. It was in this class that Thaler began to see this model as something that could predict, with 100 percent certainty, that many things in the universe, such as the universal strength of gravity, would always be true. He also started to appreciate that there were limits to the Standard Model, and that there are some things about the universe, such as dark matter, that the theory so far has failed to describe in any organized, mathematical way.</p>
<p>“This represented a totally new, flexible way of thinking of quantum field theory where you really poked and prodded it from all angles and figured out where it really breaks down,” Thaler says. “So you have these twin realizations: that certain aspects of the Standard Model are fixed and inevitable, and certain aspects are not fixed and are therefore a source of confusion and a target for future research. Those twin aspects really inspired me.”</p>
<p><strong>Knowns and unknowns</strong></p>
<p>Thaler spent three and a half years in Berkeley, California, after graduating from Harvard, working as a postdoc at the Miller Institute for Basic Research in Science at the University of California at Berkeley, and at the Lawrence Berkeley National Laboratory, which was just up the hill from the university. At the time, he was wrestling with whether to concentrate on the dynamics of behaviors that are known in the Standard Model, or explore phenemona beyond the Standard Model.</p>
<p>He was able to get a taste of both sides at Berkeley. On campus, he found that researchers tended to theorize about the more speculative, uncertain parts of the Standard Model, while researchers at the laboratory were looking in detail at more fixed phenomena.</p>
<p>“I would spend half my time on campus and half at the lab, and got the synthesis of the two, taking the shuttle bus up and down the hill,” Thaler says. “And sometimes the most exciting things are at the intersection of those two perspectives.”</p>
<p>In 2009, he applied for a faculty position at MIT and while interviewing got to talking with physics professor Richard Milner about ways to test for the existence of dark matter. From that conversation, Thaler proposed an experimental design, which has since evolved to become DarkLight, an MIT-led experiment that aims to look for “dark forces,” or interactions that are thought influence dark matter.</p>
<p><strong>Finding structure within chaos</strong></p>
<p>In January 2010, Thaler moved, “in the dead of winter,” as he recalls, from Berkeley to Cambridge, as an assistant professor in MIT’s Department of Physics. He expected a steep curve in learning how to juggle the various teaching and research responsibilities that come with being a professor. What he didn’t anticipate was how difficult it would be for him to hand over some of those responsibilities, particularly in research, to his students.&nbsp;</p>
<p>“Learning to let go and trust my students was eye-opening,” Thaler says. “The students at MIT are fantastically brilliant, and oftentimes I would have the wrong idea of how something should work. But my students have wonderfully stuck to their guns, even if I was skeptical of their results, and convinced me that they were right.”</p>
<p>At MIT, Thaler’s research has made a major impact on several areas of physics, most notably on understanding the structure and behavior of jets produced from the collision of protons at high energies. Protons are made from accumulations of subatomic particles called quarks and gluons, which are held together by a glue-like interaction called the strong force. When protons collide at significant speeds, they release sprays or jets of quarks and gluons, which can rebind into collections of subatomic particles such as pions and kaons.</p>
<p>Thaler has developed theoretical techniques to study the strong force and the structure of these jets in detail. His techniques are now being applied at the Large Hadron Collider — the largest, most powerful particle accelerator in the world, based in Geneva, Switzerland — to look for interesting physics, and even signs of dark matter.</p>
<p>“Studying these jets is a messy business,” Thaler says. “They look like they’re just chaos. But if you work your way up to the boundary of theoretical insights, you realize within that messiness, there’s structure, and you can exploit that structure to figure out what’s going on. We haven’t yet discovered dark matter in this way, but we have been able to search for it in more exquisite detail than in the past.”</p>
<p>Looking to the future, Thaler is eager to explore more uncharted territories beyond the Standard Model, and is working on theoretical designs for other experiments to detect dark matter.&nbsp;</p>
<p>“I have a responsibility to push on whatever I think I can make an impact on, and push it forward,” Thaler says. “For that, I can’t think of a better place to be than MIT, for the next however many decades.”</p>
Professor Jesse Thaler, who recently was granted tenure as an associate professor in MIT’s Department of Physics, is applying his theoretical insights to interpret data from current experiments and guide the design of future experiments.
Image: Jared CharneyCenter for Theoretical Physics, Physics, Faculty, Profile, School of ScienceTwelve from MIT honored by the American Physical Societyhttp://news.mit.edu/2017/twelve-mit-honored-american-physical-society-1031
Prize winners span six departments in the schools of Science and Engineering.Tue, 31 Oct 2017 16:50:01 -0400School of Sciencehttp://news.mit.edu/2017/twelve-mit-honored-american-physical-society-1031<p>Twelve members of the MIT community are among those recently honored with prizes and fellowships by the&nbsp;<a href="https://www.aps.org/" target="_blank">American Physical Society</a>&nbsp;(APS). The awardees include faculty, students, and alumni from the departments of Physics, Chemistry, Civil and Environmental Engineering, Mechanical Engineering, Nuclear Science and Engineering, and Chemical Engineering.</p>
<p>As the leading membership organization for physicists from academia, industry, and the national laboratories, the APS recognizes work deemed by outstanding by leading researchers in the field worldwide.</p>
<p>Each year, no more than one half of 1 percent of the society membership is recognized by their peers for election as fellows. The 2017 MIT APS fellows include:</p>
<p><a href="http://lnsp.mit.edu/r-scott-kemp/">R. Scott Kemp</a>, associate professor of nuclear science and engineering, has been named a fellow of the American Physical Society (APS). Nominated by the Forum on Physics and Society, Kemp was cited, “[f]or innovative applications of physics to arms control verification, and pivotal scientific contributions to nuclear nonproliferation diplomacy and the understanding of technology-policy interactions in international security.”</p>
<p><a href="http://web.mit.edu/preis/www/">Pedro M. Reis</a>, Gilbert W. Winslow Career Development Professor in the Department of Civil and Environmental Engineering and associate professor in the Department of Mechanical Engineering, was elected an APS fellow for his “contributions to the field of extreme mechanics, including elastic instabilities and geometrical nonlinearities.” He was also a 2017 recipient of an APS Early Career Award for this seminal research in soft matter.</p>
<p><a href="http://news.mit.edu/2017/mit-psfc-scientists-petrasso-li-seguin-win-john-dawson-award-plasma-physics-research-0802">Earlier in the year</a>, three members of MIT's Plasma Science and Fusion Center (PSFC) High-Energy-Density Physics Division — including division head and Senior Research Scientist <a href="http://www.psfc.mit.edu/people/senior-staff/richard-d-petrasso">Richard Petrasso</a>, Senior Research Scientist <a href="https://www.psfc.mit.edu/people/senior-staff/chikang-li">Chikang Li</a>, and Research Scientist <a href="https://www.psfc.mit.edu/people/scientific-staff/fredrick-seguin">Fredrick Seguin</a> — were honored with the APS John Dawson Award for Excellence in Plasma Physics Research.</p>
<p>Other recent APS award winners include:</p>
<p><a href="http://web.mit.edu/physics/people/faculty/harrow_aram.html">Aram W. Harrow</a> ’01, PhD ’05, an associate professor of physics and research in the Laboratory for Nuclear Science, received the 2018 Rolf Landauer and Charles H. Bennett Award in Quantum Computing for his “outstanding accomplishments in the mathematics of quantum information, and the development of new algorithmic primitives for quantum computers.” A faculty member of the MIT Center for Theoretical Physics since 2013, Harrow focuses on theoretical aspects of quantum computing and quantum information. In quantum information theory, he invented the concepts of “coherent classical communication” and “entanglement spread.” In 2009, Harrow received an Outstanding Referee Award from the APS.</p>
<p><a href="http://www.uta.edu/physics/pages/faculty/profiles/jones/index.html">Benjamin J.P. Jones</a> PhD ’15, an assistant professor of physics at the University of Texas at Arlington, received the 2017 Mitsuyoshi Tanaka Dissertation Award in Experimental Particle Physics for his thesis in the field of experimental neutrino physics, “Sterile Neutrinos in Cold Climates.” Jones earned his PhD under the supervision of Professor Janet Conrad in the Department of Physics and the Laboratory for Nuclear Science, and received the Department of Physics’ 2015 Martin Deutsch Award for Excellence in Experimental Particle Physics.</p>
<p><strong>Calvin Leung</strong>, a first-year PhD student in the Department of Physics, is a co-recipient of the 2017 LeRoy Apker Award, for his work as an undergraduate at Harvey Mudd College on the “development and experimental implementation of astronomical random number generators for loophole-free tests of Bell’s inequality and other applications in quantum fundamentals, astrophysics, and tests of general relativity.” Leung currently holds a National Defense Science and Engineering Graduate Fellowship and is also the recipient of the 2016 Astronaut Scholarship, the Louise and Graydon Bell Prize, the Mindlin Prize, and the Alfred B. Focke Award.</p>
<p><strong>Ian Moult PhD ’16</strong> received the 2017 J.J. and Noriko Sakurai Dissertation Award in Theoretical Particle Physics for his work “inventing powerful new observables for tagging boosted bosons, for developing new quantum field theory techniques for jet substructure calculations, and for devising new helicity operator methods to improve precision Higgs boson studies at the Large Hadron Collider.” Moult earned his PhD under the supervision of Professor Iain Stewart in the MIT Center for Theoretical Physics and received the Department of Physics’ 2015 Andrew M. Lockett Memorial Fund Award for his graduate research. He is currently a postdoctoral research associate at the University of California at Berkeley and the Lawrence Berkeley National Laboratory.</p>
<p><a href="https://nelson.mit.edu/">Keith A. Nelson</a>, Haslam and Dewey Professor of Chemistry, was a co-recipient of the <a href="http://chemistry.mit.edu/keith-nelson-awarded-2018-frank-isakson-prize-optical-effects-solids">2018 Frank Isakson Prize for Optical Effects in Solids</a> for his “pioneering contributions to the development and application of ultra-fast optical spectroscopy to condensed matter systems, and providing insight into lattice dynamics, structural phase transitions, and the non-equilibrium control of solids.” Nelson is a fellow of the American Association for the Advancement of Science, the Optical Society of America, and the American Physical Society, a member of the American Academy of Arts and Sciences, and has received the Coblentz, Lippincott, Zewail, and Bomem-Michelson awards.</p>
<p><a href="https://cheme.scripts.mit.edu/olsenlab/">Bradley D. Olsen</a> ’03, Paul M. Cook Career Development Professor of Chemical Engineering, was awarded the 2018 John H. Dillon Medal for his work “significantly expanding our understanding of the physics of polymers, including the self-assembly of block copolymers incorporating a fully folded protein, the influence of polymer shape on diffusion; for engineering novel gels; and for updating the theory of the modulus of a network.” Olsen’s previous honors include an Alfred P. Sloan Research Fellowship, the DuPont Young Professor Award and the Allan P. Colburn Award; he was named a Kavli Foundation Emerging Leader in Chemistry in 2017.</p>
<p><a href="https://www.aps.org/programs/honors/prizes/prizerecipient.cfm?first_nm=Jonathan&amp;last_nm=Ouellet&amp;year=2017">Jonathan Loren Ouellet</a>, a postdoctoral researcher at MIT working in the Professor Lindley Winslow’s group in the Laboratory for Nuclear Science, received the 2017 Dissertation Award in Nuclear Physics for “his outstanding contributions to the search for neutrinoless double beta decay of 130Te, and setting a new limit on its decay half-life, at the Cryogenic Underground Observatory for Rare Events in Gran Sasso, Italy.” At MIT, he has recently begun working on a new cryogenic-based axion dark matter search, called ABRACADABRA.</p>
Clockwise from top left: Aram Harrow, Benjamin Jones, Scott Kemp, Calvin Leung, Ian Moult, Keith Nelson, Bradley Olsen, Jonathan Loren Ouellet, and Pedro ReisImage courtesy of the School of ScienceAwards, honors and fellowships, School of Science, School of Engineering, Physics, Nuclear science and engineering, Civil and environmental engineering, Plasma Science and Fusion Center, Laboratory for Nuclear Science, Chemistry, Chemical engineering, Mechanical engineering, Faculty, Graduate, postdoctoral, Alumni/aeJerry Akinsulire: The making of a maker mentorhttp://news.mit.edu/2017/olorunsola-jerry-akinsulire-maker-mentor-in-nuclear-science-and-engineering-1026
Undergraduate Olorunsola “Jerry” Akinsulire spearheads a new builder space in the Department of Nuclear Science and Engineering.Thu, 26 Oct 2017 17:25:00 -0400Leda Zimmerman | Department of Nuclear Science and Engineeringhttp://news.mit.edu/2017/olorunsola-jerry-akinsulire-maker-mentor-in-nuclear-science-and-engineering-1026<p>Although he has operated MIT’s nuclear research reactor and worked as an intern for a national energy laboratory, senior Olorunsola “Jerry” Akinsulire never&nbsp;seems&nbsp;happier than when he's&nbsp;demonstrating the use of machine tools to fellow students, soldering iron in hand.</p>
<p>“It’s very exciting helping others develop their projects and being someone people can look up to,” says Akinsulire, a double major in nuclear science and engineering&nbsp;and physics.</p>
<p>As a leader in the development and soon, operation, of a new “makerspace” for the Department of Nuclear Science and Engineering (NSE), Akinsulire spends time doing what he most enjoys: collaborative, hands-on work in his field. This year he will serve as an official mentor to NSE undergraduates in a fabrication facility that he helped create.</p>
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<p>“We really need this student space in nuclear engineering,” he says. “For most of the department’s project classes, when you have to manufacture something you must go somewhere else, and now we can do the work here.”</p>
<p>Akinsulire’s involvement in the NSE makerspace venture evolved from a series of his own maker opportunities. During freshman year Independent Activities Period, he built a Geiger counter in a course with Assistant Professor&nbsp;<a href="http://web.mit.edu/nse/people/faculty/short.html" target="_blank">Michael Short</a>. As a high school student Akinsulire had built robots for the FIRST Tech Challenge, but this was different. “It was exciting soldering and working with electric components for the first time,” he says.</p>
<p>Akinsulire’s next major maker opportunity arrived sophomore year in 22.012 (Seminar in Fusion and Plasma Physics), taught by&nbsp;<a href="http://web.mit.edu/nse/people/faculty/white.html" target="_blank">Anne White</a>, the Cecil and Ida Green Associate Professor in Nuclear Engineering. For a class presentation, Akinsulire and a partner described the structure and function of a fusor, the device that confines plasma in an electrostatic field.</p>
<p>“When we finished, Professor White told us that if we were interested, we could totally build one,” Akinsulire recalls. “We said, ‘Really?’ She said, ‘Really!’”</p>
<p>After researching components from vacuum chamber to pump to power supply, and figuring out how to design an electrode to trigger a fusion reaction, Akinsulire and a partner, with a graduate student mentor, assembled their own fusor. Watching argon gas turn purple as the voltage from the electrode in the confinement chamber increased, Akinsulire says “was like magic.”</p>
<p>This side research project earned Akinsulire and his team a poster presentation slot at the 58th annual meeting of the American Physics Society Division of Plasma Physics in the fall of 2016.</p>
<p>After this experience, Akinsulire “wanted to take things further,” he says. White obliged, inviting him to help develop a nuclear engineering makerspace.</p>
<p>Akinsulire spent the summer of 2016 devising safety guidelines, operating procedures, and layout for every machine shop tool that might come into play in a future NSE facility. He also developed simple projects for students new to making their own devices.</p>
<p>“Many students here focus exclusively on science and theory, but they need to translate ideas to prototypes, and use equipment to test and simulate,” he says. “It’s important for all students to become comfortable in the machine shop, to go from project design to something they can physically hold.”</p>
<p>Having made this journey himself, Akinsulire is eager to assist fellow students. He knows from his own experience how critical support can be, whether in a maker space or a classroom: During his pre-college instruction in MIT’s Minority Introduction to Engineering and Science&nbsp;program, “the Physics II math was really challenging, and I thought I couldn’t do it,” recalls Akinsulire. “With my TA’s encouragement, I stuck with it, and ended up the top student in the class.”</p>
<p>This achievement reinforced Akinsulire’s belief that MIT was the right place for him, and nuclear engineering the right field. It helped validate a goal that had emerged during his AP Chemistry class at the Queens High School for the Sciences. “I vividly remember my teacher covering fission and fusion, talking about the impact of global warming, and how clean nuclear energy could help the environment,” he says. “I decided then that this was the path I wanted to go down.”</p>
<p>When Akinsulire arrived on campus, he was determined to investigate as many opportunities in nuclear science and engineering as he could fit in his schedule. In freshman year, he signed up for the student operator program with MIT’s&nbsp;Nuclear Reactor Laboratory. This led to a summer of instruction in reactor physics and training in basic reactor functions. More recently, Akinsulire interned at the Argonne National Lab. His research focused on using RFID tags and wireless sensor networks as part of a new safety system being developed for remote monitoring of radiation in nuclear reactors.</p>
<p>Although independent projects, research internships, classes, and maker mentoring don’t leave much spare time, Akinsulire manages to blow off steam with a Senegalese drumming group called Rambax, a campus dance troupe, and with fraternity friends.</p>
<p>After graduating next spring, Akinsulire will continue with master’s studies at NSE. He hasn’t yet decided where his academic journey will ultimately lead, but he has some ideas, including designing a new reactor core and “contributing to the next big jump forward in the nuclear industry.” Akinsulire’s ideal job would involve “an interplay — developing ideas on a drawing board, building something hands on, and then testing in the world,” he says.</p>
<p>“That would be the perfect combination for me.”</p>
Jerry Akinsulire’s ideal job would involve “an interplay — developing ideas on a drawing board, building something hands on, and then testing in the world,” he says. “That would be the perfect combination for me.”Photo: Gretchen ErtlSchool of Engineering, Energy, Students, Nuclear power and reactors, Nuclear science and engineering, Renewable energy, maker movement, Profile, Undergraduate, Physics, School of ScienceOcean sound waves may reveal location of incoming objectshttp://news.mit.edu/2017/ocean-sound-waves-may-reveal-location-incoming-objects-1026
New acoustic analysis could pinpoint impacts by meteorites or possibly plane debris.Thu, 26 Oct 2017 00:00:01 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/ocean-sound-waves-may-reveal-location-incoming-objects-1026<p>The ocean can seem like an acoustically disorienting place, with muffled sounds from near and far blending together in a murky sea of noise.</p>
<p>Now an MIT mathematician has found a way to cut through this aquatic cacaphony, to identify underwater sound waves generated by objects impacting the ocean’s surface, such as debris from meteorites or aircraft. The results are published this week in the online journal <em>Scientific Reports</em>.</p>
<p>Lead author Usama Kadri, a research affiliate in MIT’s Department of Mathematics, is applying the team’s acoustic analysis in hopes of locating Malaysia Airlines flight 370, an international passenger plane that disappeared over the southern Indian Ocean on March 8, 2014.</p>
<p>Since the aircraft’s disappearance, authorities have confirmed and recovered a few of the plane’s parts. However, the bulk of the aircraft has yet to be identified, as has any reasonable explanation for its demise.</p>
<p>Kadri believes that if the plane indeed crashed into the ocean, it would have generated underwater sound waves, called acoustic-gravity waves, with a very specific pattern. Such waves travel across large distances before dissipating and therefore would have been recorded by hydrophones around the world. If such patterns can be discerned amid the ocean’s background noise, Kadri says acoustic-gravity waves can be traced back to the location of the original crash.</p>
<p>In this new paper, Kadri and his colleagues have identified a characteristic pattern of acoustic-gravity waves produced by impacting objects, as opposed to other sources such as earthquakes or underwater explosions. They have looked for this pattern in data collected by underwater microphones near Australia on March 8, 2014, within the time window when the plane disappeared.</p>
<p>The team picked out two weak signals likely produced on that date by two ocean-impacting objects. The researchers determined, however, that the locations of these impacts were too far away from the course that the plane is believed to have taken. Instead, the impacts may have been produced by small meteorites falling into the sea. Kadri says that if the entire plane had crashed into the ocean, it would have produced a much stronger, clearer signal.</p>
<p>“The fact that there was no strong signature might suggest that at least some parts were detached from the airplane before impacting,” Kadri says. “With better data filtering, we may be able to revisit the Malaysia Airlines mystery and to try to identify other possible signals.”</p>
<p>The paper’s co-authors include researchers from Cardiff University, where Kadri also serves as a lecturer, and Memorial University of Newfoundland.</p>
<p><strong>At the speed of sound</strong></p>
<p>Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. These waves can travel hundreds of miles across the deep ocean at the speed of sound before dissipating.</p>
<p>Kadri and his colleagues carried out experiments to see whether objects hitting the water’s surface produced a characteristic pattern in acoustic-gravity waves. They dropped 18 weighted spheres into a large water tank, from various heights and locations, and recorded the resulting acoustic-gravity waves using a hydrophone.</p>
<p>For each impact, the team observed a similar sound wave profile, consisting of three main parts.</p>
<p>“We found there was a very special structure to these impacting objects,” Kadri says. “The first part seems to be the initial impact itself, followed by the second part — as the object enters the water, it traps some air, which eventually rises back to the surface. The last part seems to be secondary waves that impact the bottom of the tank, before reflecting back up.”</p>
<p>The researchers then developed a mathematical model to relate a particular pattern of acoustic-gravity waves to certain properties of its source, such as its original location, time of occurrence, duration, and speed of impact. They found the model accurately calculated the location and time of two recent earthquakes, using acoustic-gravity wave data from nearby hydrophones.</p>
<p>After verifying the model, the team used it to try and locate evidence of the Malaysia Airlines plane crash. The researchers first looked through data from the Comprehensive Nuclear-Test-Ban Treaty Organization’s three hydrophone stations off the coast of western Australia. The data were collected within an 18-hour time window on March 8, 2014.</p>
<p><strong>A mystery continues</strong></p>
<p>The researchers focused on a two-hour period, between 0:00 and 02:00 UTC, during which the plane is believed to have crashed in the southern Indian Ocean. They identified two “remarkably weak” signals, according to Kadri, each with an acoustic-gravity wave pattern similar to those created by impacting objects.</p>
<p>The first event was recorded only a few minutes after the last transmission time between the aircraft and a monitoring satellite. However, the researchers determined the event occurred about 500 kilometers away from the plane’s last known location. The aircraft would have had to fly faster than 3,300 kilometers per hour for nine minutes — an unlikely scenario.</p>
<p>The second event occurred closer to the plane’s presumed path, about an hour after the plane’s last transmission. While the signal is too weak to confidently decipher, the researchers suggest that it could have been produced by a “delayed implosion or impact with the sea floor.”</p>
<p>Given the timing and locations of the two events, however, it is more likely that they were generated by falling meteorites. As the team notes in their paper, between 18,000 and 84,000 meteorites bigger than 10 grams fall to Earth each year. If the two signals were indeed produced by meteorites, they would have been relatively large in mass.</p>
<p>The team has submitted its analysis to the Australian Transport Safety Bureau, which led the investigation into flight 370. In the meantime, the researchers plan to apply their method to locate and study other acoustic-gravity wave sources.</p>
<p>“We have a method that we can use to identify general events in the ocean, and we can do that to a high degree of accuracy from a single hydrophone station,” Kadri says. “These events can be an earthquake, an underwater explosion, a falling meteorite, or a plane crash.”</p>
Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. Usama Kadri and his colleagues carried out experiments to see whether objects hitting a water’s surface produced a characteristic pattern in acoustic-gravity waves.
Image: Jose-Luis Olivares/MITFluid dynamics, Mathematics, Oceanography and ocean engineering, Physics, Research, School of Science, WaterScientists detect comets outside our solar systemhttp://news.mit.edu/2017/scientists-detect-comets-outside-our-solar-system-1026
Team of professional and citizen scientists identifies tails of comets streaking past a distant star.Wed, 25 Oct 2017 23:59:59 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/scientists-detect-comets-outside-our-solar-system-1026<p>Scientists from MIT and other institutions, working closely with amateur astronomers, have spotted the dusty tails of six exocomets — comets outside our solar system — orbiting a faint star 800 light years from Earth.</p>
<p>These cosmic balls of ice and dust, which were about the size of Halley’s Comet and traveled about 100,000 miles per hour before they ultimately vaporized, are some of the smallest objects yet found outside our own solar system.</p>
<p>The discovery marks the first time that an object as small as a comet has been detected using transit photometry, a technique by which astronomers observe a star’s light for telltale dips in intensity. Such dips signal potential transits, or crossings of planets or other objects in front of a star, which momentarily block a small fraction of its light. &nbsp;</p>
<p>In the case of this new detection, the researchers were able to pick out the comet’s tail, or trail of gas and dust, which blocked about one-tenth of 1 percent of the star’s light as the comet streaked by.&nbsp;</p>
<p>“It’s amazing that something several orders of magnitude smaller than the Earth can be detected just by the fact that it’s emitting a lot of debris,” says Saul Rappaport, professor emeritus of physics in MIT’s Kavli Institute for Astrophysics and Space Research. “It’s pretty impressive to be able to see something so small, so far away.”</p>
<p>Rappaport and his team have published their results this week in the <em>Monthly Notices of the Royal Astronomical Society. </em>The paper’s co-authors are Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics; several amateur astronomers including Thomas Jacobs of Bellevue, Washington; and researchers from the University of Texas at Austin, NASA’s Ames Research Center, and Northeastern University.</p>
<p><strong>“Where few have traveled”</strong></p>
<p>The detection was made using data from NASA’s Kepler Space Telescope, a stellar observatory that was launched into space in 2009. For four years, the spacecraft monitored about 200,000 stars for dips in starlight caused by transiting exoplanets.</p>
<p>To date, the mission has identified and confirmed more than 2,400 exoplanets, mostly orbiting stars in the constellation Cygnus, with the help of &nbsp;automated algorithms that quickly sift through Kepler’s data, looking for characteristic dips in starlight.</p>
<p>The smallest exoplanets detected thus far measure about one-third the size of the Earth. Comets, in comparison, span just several football fields, or a small city at their largest, making them incredibly difficult to spot.</p>
<p>However, on March 18, Jacobs, an amateur astronomer who has made it his hobby to comb through Kepler’s data, was able to pick out several curious light patterns amid the noise.</p>
<p>Jacobs, who works as an employment consultant for people with intellectual disabilities by day, is a member of the Planet Hunters — a citizen scientist project first established by Yale University to enlist amateur astronomers in the search for exoplanets. Members were given access to Kepler’s data in hopes that they might spot something of interest that a computer might miss.</p>
<p>In January, Jacobs set out to scan the entire four years of Kepler’s data taken during the main mission, comprising over 200,000 stars, each with individual light curves, or graphs of light intensity tracked over time. Jacobs spent five months sifting by eye through the data, often before and after his day job, and through the weekends.</p>
<p>“Looking for objects of interest in the Kepler data requires patience, persistence, and perseverance,” Jacobs says. “For me it is a form of treasure hunting, knowing that there is an interesting event waiting to be discovered. It is all about exploration and being on the hunt where few have traveled before.”</p>
<p><strong>“Something we’ve seen before”</strong></p>
<p>Jacobs’ goal was to look for anything out of the ordinary that computer algorithms may have passed over. In particular, he was searching for single transits — dips in starlight that happen only once, meaning they are not periodic like planets orbiting a star multiple times.</p>
<p>In his search, he spotted three such single transits around KIC 3542116, a faint star located 800 light years from Earth (the other three transits were found later by the team). He flagged the events and alerted Rappaport and Vanderburg, with whom he had collaborated in the past to interpret his findings.</p>
<p>“We sat on this for a month, because we didn’t know what it was — planet transits don’t look like this,” Rappaport recalls. “Then it occurred to me that, ‘Hey, these look like something we’ve seen before.’”</p>
<p>In a typical planetary transit, the resulting light curve resembles a “U,” with a sharp dip, then an equally sharp rise, as a result of a planet first blocking a little, then a lot, then a little of the light as it moves across the star. However, the light curves that Jacobs identified appeared asymmetric, with a sharp dip, followed by a more gradual rise.</p>
<p>Rappaport realized that the asymmetry in the light curves resembled disintegrating planets, with long trails of debris that would continue to block a bit of light as the planet moves away from the star. However, such disintegrating planets orbit their star, transiting repeatedly. In contrast, Jacobs had observed no such periodic pattern in the transits he identified.</p>
<p>“We thought, the only kind of body that could do the same thing and not repeat is one that probably gets destroyed in the end,” Rappaport says.</p>
<p>In other words, instead of orbiting around and around the star, the objects must have transited, then ultimately flown too close to the star, and vaporized.</p>
<p>“The only thing that fits the bill, and has a small enough mass to get destroyed, is a comet,” Rappaport says.</p>
<p>The researchers calculated that each comet blocked about one-tenth of 1 percent of the star’s light. To do this for several months before disappearing, the comet likely disintegrated entirely, creating a dust trail thick enough to block out that amount of starlight.</p>
<p>Vanderburg says the fact that these six exocomets appear to have transited very close to their star in the past four years raises some intriguing questions, the answers to which could reveal some truths about our own solar system.</p>
<p>“Why are there so many comets in the inner parts of these solar systems?” Vanderburg says. “Is this an extreme bombardment era in these systems? That was a really important part of our own solar system formation and may have brought water to Earth. Maybe studying exocomets and figuring out why they are found around this type of star … could give us some insight into how bombardment happens in other solar systems.”</p>
<p>The researchers say that in the future, the MIT-led Transiting Exoplanet Survey Satellite (TESS) mission will continue the type of research done by Kepler.</p>
<p>Apart from contributing to the fields of astrophysics and astronomy, Rappaport says, the new detection speaks to the perserverence and discernment of citizen scientists.</p>
<p>“I could name 10 types of things these people have found in the Kepler data that algorithms could not find, because of the pattern-recognition capability in the human eye,” Rappaport says. “You could now write a computer algorithm to find this kind of comet shape. But they were missed in earlier searches. They were deep enough but didn’t have the right shape that was programmed into algorithms. I think it’s fair to say this would never have been found by any algorithm.”</p>
<p>This research made use of data collected by the Kepler mission, funded by the NASA Science Mission directorate.</p>
An artist’s conception of a view from within the Exocomet system KIC 3542116.Image: Danielle FutselaarAstronomy, Astrophysics, Kavli Institute, NASA, Physics, Research, Satellites, School of Science, space, Space, astronomy and planetary scienceMaterial could bring optical communication onto silicon chipshttp://news.mit.edu/2017/ultrathin-films-semiconductor-optical-communication-silicon-chips-1023
Ultrathin films of a semiconductor that emits and detects light can be stacked on top of silicon wafers.Mon, 23 Oct 2017 10:59:59 -0400Helen Knight | MIT News Officehttp://news.mit.edu/2017/ultrathin-films-semiconductor-optical-communication-silicon-chips-1023<p>The huge increase in computing performance in recent decades has been achieved by squeezing ever more transistors into a tighter space on microchips.</p>
<p>However, this downsizing has also meant packing the wiring within microprocessors ever more tightly together, leading to effects such as signal leakage between components, which can slow down communication between different parts of the chip. This delay, known as the “interconnect bottleneck,” is becoming an increasing problem in high-speed computing systems.</p>
<p>One way to tackle the interconnect bottleneck is to use light rather than wires to communicate between different parts of a microchip. This is no easy task, however, as silicon, the material used to build chips, does not emit light easily, according to Pablo Jarillo-Herrero, an associate professor of physics at MIT.</p>
<p>Now, in a paper published today in the journal <em>Nature Nanotechnology</em>, researchers describe a light emitter and detector that can be integrated into silicon CMOS chips. The paper’s first author is MIT postdoc Ya-Qing Bie, who is joined by Jarillo-Herrero and an interdisciplinary team including Dirk Englund, an associate professor of electrical engineering and computer science at MIT.</p>
<p>The device is built from a semiconductor material called molybdenum ditelluride. This ultrathin semiconductor belongs to an emerging group of materials known as two-dimensional transition-metal dichalcogenides.</p>
<p>Unlike conventional semiconductors, the material can be stacked on top of silicon wafers, Jarillo-Herrero says.</p>
<p>“Researchers have been trying to find materials that are compatible with silicon, in order to bring optoelectronics and optical communication on-chip, but so far this has proven very difficult,” Jarillo-Herrero says. “For example, gallium arsenide is very good for optics, but it cannot be grown on silicon very easily because the two semiconductors are incompatible.”</p>
<p>In contrast, the 2-D molybdenum ditelluride can be mechanically attached to any material, Jarillo-Herrero says.</p>
<p>Another difficulty with integrating other semiconductors with silicon is that the materials typically emit light in the visible range, but light at these wavelengths is simply absorbed by silicon.</p>
<p>Molybdenum ditelluride emits light in the infrared range, which is not absorbed by silicon, meaning it can be used for on-chip communication.</p>
<p>To use the material as a light emitter, the researchers first had to convert it into a P-N junction diode, a device in which one side, the P side, is positively charged, while the other, N side, is negatively charged.</p>
<p>In conventional semiconductors, this is typically done by introducing chemical impurities into the material. With the new class of 2-D materials, however, it can be done by simply applying a voltage across metallic gate electrodes placed side-by-side on top of the material.</p>
<p>“That is a significant breakthrough, because it means we do not need to introduce chemical impurities into the material [to create the diode]. We can do it electrically,” Jarillo-Herrero says.</p>
<p>Once the diode is produced, the researchers run a current through the device, causing it to emit light.</p>
<p>“So by using diodes made of molybdenum ditelluride, we are able to fabricate light-emitting diodes (LEDs) compatible with silicon chips,” Jarillo-Herrero says.</p>
<p>The device can also be switched to operate as a photodetector, by reversing the polarity of the voltage applied to the device. This causes it to stop conducting electricity until a light shines on it, when the current restarts.</p>
<p>In this way, the devices are able to both transmit and receive optical signals.</p>
<p>The device is a proof of concept, and a great deal of work still needs to be done before the technology can be developed into a commercial product, Jarillo-Herrero says.</p>
<p>This paper fills an important gap in integrated photonics, by realizing a high-performance silicon-CMOS-compatible light source, says Frank Koppens, a professor of quantum nano-optoelectronics at the Institute of Photonic Sciences in Barcelona, Spain, who was not involved in the research.</p>
<p>“This work shows that 2-D materials and Si-CMOS and silicon photonics are a natural match, and we will surely see many more applications coming out of this [area] in the years to come,” Koppens says.</p>
<p>The researchers are now investigating other materials that could be used for on-chip optical communication.</p>
<p>Most telecommunication systems, for example, operate using light with a wavelength of 1.3 or 1.5 micrometers, Jarillo-Herrero says.</p>
<p>However, molybdenum ditelluride emits light at 1.1 micrometers. This makes it suitable for use in the silicon chips found in computers, but unsuitable for telecommunications systems.</p>
<p>“It would be highly desirable if we could develop a similar material, which could emit and detect light at 1.3 or 1.5 micrometers in wavelength, where telecommunication through optical fiber operates,” he says.</p>
<p>To this end, the researchers are exploring another ultrathin material called black phosphorus, which can be tuned to emit light at different wavelengths by altering the number of layers used. They hope to develop devices with the necessary number of layers to allow them to emit light at the two wavelengths while remaining compatible with silicon.</p>
<p>“The hope is that if we are able to communicate on-chip via optical signals instead of electronic signals, we will be able to do so more quickly, and while consuming less power,” Jarillo-Herrero says.</p>
<p>The research was supported by Center for Excitonics, an EFRC funded by the U.S. Department of Energy.</p>
Researchers have designed a light-emitter and detector that can be integrated into silicon CMOS chips. This illustration shows a molybdenum ditelluride light source for silicon photonics.
Image: Sampson WilcoxResearch, Physics, Electrical Engineering & Computer Science (eecs), Nanoscience and nanotechnology, Computer science and technology, Photonics, School of Science, School of EngineeringMIT researchers discuss the new &quot;multi-messenger&quot; era of astrophysics researchhttp://news.mit.edu/2017/mit-researchers-discuss-LIGO-event-astrophysics-research-1018
Mavalvala, Evans, Frebel, Katsavounidis, and Vitale discuss the science behind LIGO&#039;s observations of a neutron star collision.Wed, 18 Oct 2017 16:50:01 -0400Julia C. Keller | School of Sciencehttp://news.mit.edu/2017/mit-researchers-discuss-LIGO-event-astrophysics-research-1018<p>On Monday, Oct.&nbsp;16, scientists from the National Science Foundation (NSF), representatives from the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration, and other researchers from ground-based&nbsp;and space-based observatories around the world announced the detection of GW170817 — gravitational waves resulting from the merger of two neutron stars.</p>
<p>This detection was the first correlation between gravitational waves and electromagnetic signals in the form of gamma ray bursts and X-ray, ultraviolet, optical, infrared, and radio waves.</p>
<p>Following the <a href="http://www.youtube.com/c/VideosatNSF/live" target="_blank">live webcast</a> of the announcement made from the National Press Club in Washington,&nbsp;MIT President L. Rafael Reif opened the remarks for an on-campus panel.</p>
<p>“Today is a wonderful reminder that investing in basic science is investing in our nation’s future,”&nbsp;he&nbsp;told the crowd&nbsp;in the Vannevar Bush Room.&nbsp;</p>
<p>Reif then acknowledged the vision of luminaries like&nbsp;Bush, the former MIT dean of engineering, who helped establish what would later become the NSF, the funding agency that has&nbsp;supported the development of the LIGO and Advanced LIGO projects over many decades.</p>
<p>“Bush and his colleagues understood that that basic science can be electrifying, revolutionary, and catalytic. But they also knew that the work that produces fundamental breakthroughs is painstaking, rigorous, and slow,” he said. “For that reason, basic science requires the deep, steady support that only government can provide.”</p>
<p>Reif then introduced Nergis Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics —&nbsp;“a LIGO pioneer in her own right” — who began her career as a graduate student of MIT Professor Emeritus Rainer Weiss, the winner of the 2017 Nobel Prize in physics for his work on LIGO.&nbsp;</p>
<p>Mavalvala led a panel of MIT scientists in a discussion of the science of the discovery and of its importance in opening up a new field of astronomical discovery.</p>
<p><strong>Multi-messenger&nbsp;astronomy</strong></p>
<p>“I’d always believed that gravitational waves would reveal more of the universe to us — that there would be many more discoveries. But I have to say that I didn’t imagine that it would be quite so soon and certainly not as spectacular,” said Mavalvala. “The combination of gravitational waves and electromagnetic observation, the show that we’ve put together of sound and light, has really blown away most of us in the field.”&nbsp;</p>
<p>The inspiraling of the neutron stars produced gravitational waves that were detected for more than a minute with the LIGO detectors, and the additional “messengers” from the event, in the form of visible light and X-ray and radio waves, lasted for days after the cataclysmic event.</p>
<p>The neutron star merger occurred as part of the constellation we know as Hydra in the galaxy NGC4993, only 130 million light years away as compared with LIGO and Virgo’s most recent black hole merger detection nearly 1.8 billion light years away.<br />
&nbsp;<br />
Mavalvala said the researchers had heard scientists at the DC press event say that the event happened&nbsp;in “a galaxy far away,’” but by astronomers’ standards, it&nbsp;actually happened in a galaxy “near away.”</p>
<p><strong>We are made of “neutron star stuff”</strong></p>
<p>The astronomical event also confirmed the theory that the collision of these super dense neutron stars produced elements heavier than iron in the periodic table. Mavalvala first asked Anna Frebel, the Silverman (1968) Family Career Development Associate Professor of Physics, to speak about the neutron start collision as the “factories where these heavy elements are produced.”</p>
<p>Frebel began with the famous quote from Carl Sagan: “We are made from star stuff.”&nbsp;</p>
<p>“After today, we know a lot more about what that ‘star stuff actually’ is and how it’s made,” said Frebel, who is not on the LIGO or Virgo teams. “We can confidently add ‘and neutron star stuff’” to the list of what humans are made from, she said.</p>
<p>To create elements heavier than iron, neutrons must bombard something like an iron nucleus that would ultimately decay and form a stable element like silver or gold. “When you have two neutron stars colliding, you have neutrons galore,” said Frebel. “We had indication before [this event detection] that only neutron star merger can produce these elements. No other site has enough ‘oopmf.’”</p>
<p>The importance of this merger event, said Frebel, is that “we can actually see element formation in action.”</p>
<p>In the decay of these neutron-rich isotopes to stable elements, light is emitted and can be can be observed with light-collecting telescopes as a “‘kilonova’, this afterglow of element production,” she said. Though the creation of the isotopes only takes one or two seconds, Frebel said, the decay to stable elements take a couple weeks to occur. Scientists therefore have a long window to be able to make observations of this event.&nbsp;</p>
<p>Erik Katsavounidis, a senior research scientist in MIT’s Kavli Institute for Astrophysics and Space Research, added that the event “is not just a gold&nbsp;mine scientifically, but it’s literally a gold mine that we’ve just discovered.”&nbsp;</p>
<p>Katsavounidis then responded to a question about whether the event shed new insight into the rate of formation of these neutron star mergers given the amount of heavy elements, such as gold and platinum, present in the Earth’s crust.&nbsp;</p>
<p>Though it was known that supernovae could produce heavier elements, said Katsavounidis, astrophysicists theorized that only a kilonova produced by a binary neutron star merger could produce the abundance of those elements in our solar system.&nbsp;</p>
<p>Salvatore Vitale, an assistant professor of physics, continued the discussion by commenting on the rate of discovery of these events.&nbsp;</p>
<p>“Once LIGO is at its full design sensitivity,” said Vitale, “it would be on the order of 40 to 50 neutron stars per year.”</p>
<p>“We have about a factor of 2 to go from the current sensitivity and the design and that corresponds to roughly a factor of 10 in terms of the rate,” said Matthew Evans, the D. Reid Weedon, Jr. '41 Career Development Professor of Physics and an expert in the design of the interferometers.&nbsp;</p>
<p>“It’s not strange that we saw one of these with our current sensitivity,” said Evans, “But as we go forward with the design, we’ll have several per year.”&nbsp;</p>
<p>Katsavounidis clarified that the rate of detecting an event similar to GW170817 is still unknown because it’s not a given that a neutron star merger would necessarily be accompanied by electromagnetic radiation as seen in this most recent event.</p>
<p>In addition to shedding light on the formation of heavy elements and the rate at which scientists predict these types of events might occur, Mavalvala later added that the detection solves a “decades-long mystery” of the origin of short-duration gamma ray bursts. The Fermi Gamma-ray Space telescope recorded a gamma ray burst on Aug. 17, performing just as intended and as it does with bursts that occur more than 200 times a year. The difference was the near-simultaneous gravitational-wave detection from the LIGO-Virgo global network of interferometers that linked the two events.</p>
<p>When asked about how more than 70 space research labs and telescopes could have so quickly coordinated to observe this event, Katsavounidis said that a coordinated effort was put into place beginning more than 10 years ago for rapid analysis, coordination, and communication.&nbsp;</p>
<p>He then showed a slide of how the event unfolded over time from first the gravitational wave signal lasting just over a minute to electromagnetic radiation that could be observed for days to weeks after the event.</p>
<p>“[It’s like] you’re staring at Van Gogh’s Starry Night and there are 11 swirly stars,” said Katsavounidis. “And you’re listening to Benny Goodman do the glissando at the opening [of Gershwin ‘Rhapsody in Blue’] and then you see the 12th swirly star.”&nbsp;</p>
<p>As to whether the final object in the sky is, in fact, another neutron star or a black hole is currently a puzzle for astronomers to work out. “[The answer] depends on how squishy the neutron stars are and how much mass they can support before they collapse into a black hole,” said Vitale. “That’s one of the things we don’t know yet."</p>
Members of MIT's panel on the LIGO observation of a merger of neutron stars, (left to right) Anna Frebel, Salvatore Vitale, Nergis Mavalvala, Erik Katsavounidis, and Matthew Evans, pose for a photo at the Oct. 16 event.Photo: Jake BelcherSchool of Science, Astronomy, Astrophysics, Kavli Institute, Stars, Space, astronomy and planetary science, National Science Foundation (NSF), LIGO, Chemistry, Special events and guest speakers, PhysicsBridging the science-policy dividehttp://news.mit.edu/2017/student-profile-talia-weiss-1018
For MIT senior Talia Weiss, physics and theater have provided a springboard for new interests in political science. Tue, 17 Oct 2017 23:59:59 -0400Fatima Husain | MIT News correspondenthttp://news.mit.edu/2017/student-profile-talia-weiss-1018<p>In the eighth grade, in response to being asked what she wanted to be when she grew up, Talia Weiss critically examined her aspirations and gathered them into one succinct statement: “I wanted to be a writer, dancer, and an astrophysicist,” she recalls. Weiss, now an MIT senior majoring in physics, can comfortably say she’s stuck to her goals, save for a little variation.</p>
<p>During her time at MIT, Weiss’ diverse interests — in physics, political science, and theater — have ultimately converged; she is now on mission to help close the gap between scientific and political thinkers, including scientists and policymakers in&nbsp;government.</p>
<p>Before arriving at MIT, where her interest in political science developed, Weiss spent her teenage years pursuing a passion for physics. “I found diaries from 7th grade where I asked a whole stream of questions about the universe and the ‘edge of the universe’ and its expansion,” she says.</p>
<p>She also looked for answers, spending time on Wikipedia researching black holes, the physical world, and the nature of the universe. Her curiosity led her to spend her high school summers at Northwestern University, where she conduced astrophysics research for three years on an anomalous type of galaxy.</p>
<p>“The fact that my research project was so fun was further&nbsp;indication that I should keep pursuing physics for a while,” she says.</p>
<p><strong>Theoretically assertive</strong></p>
<p>Indeed, she continued with physics at MIT even before her freshman classes began. At PhysPOP, a freshman preorientation program run by physics undergraduate students, Weiss attended a talk by David Kaiser, the Germeshausen Professor of the History of Science and professor of physics.</p>
<p>Though freshmen didn’t usually pursue theoretical physics research projects through the Undergraduate Research Opportunities Program (UROP) until they had taken a few classes, Weiss was determined to get involved immediately in the research Kaiser described. “Not only was his research exciting, but he was so personable and so passionate and so able to explain the material that I was taken by it. I went up and asked him for a UROP right afterward,” she says.</p>
<p>She likens her experiences as a freshman undertaking a UROP in quantum mechanics to drinking from the firehose, a common expression used to describe academics and activities at MIT. Luckily, as she puts it, she had support from her research advisors including Kaiser and Joseph Formaggio, an associate professor in the Department of Physics and the Laboratory for Nuclear Science, as well as from the graduate students and postdocs in her lab.</p>
<p>With 18 months of quantum mechanics and particle physics research under her belt by junior year, Weiss enrolled in Junior Lab, a two-semester experimental physics sequence in which students recreate historical physics experiments each month. At the end of the optional second course in the sequence, students design an experimental apparatus to test a topic of their choice. Weiss and her partner focused in on parity, which refers to a transformation that flips the right- or left-handedness of a coordinate system in quantum mechanics.</p>
<p>“We were working on putting together an experiment that had originally been conducted in the late ’50s, including by someone who is a professor emeritus at MIT,” says Weiss, referring to nuclear physicist Lee Grodzins.</p>
<p>When Grodzins heard Weiss and her partner were recreating his experiment, he visited them at the Junior Lab. “When he heard we were recreating his study, he was so enthusiastic that he graciously visited to&nbsp;assist us with our theoretical and experimental questions,” she says. “That’s a very MIT-like&nbsp;experience — one you can’t find in many other places.”</p>
<p>While visiting the students in the lab, Grodzins also recounted tales of his career. “He also would tell us about what it was like being at Brookhaven [National Laboratory] during the Cold War era. It sounded like a really exciting time to be doing physics,” Weiss says.</p>
<p><strong>Performing on and off stage</strong></p>
<p>Though her research community remains her “home base,” Weiss has also been active in MIT’s theater scene and its Jewish community, through MIT Hillel.</p>
<p>From Dramashop, to the Musical Theater Guild, to the Shakespeare Ensemble, “I’ve been engaged with almost all the different theater communities at some point,” she says.</p>
<p>After Rabbi Gavriel Goldfeder, the senior Jewish educator at MIT Hillel, reached out to students for ideas that could lead to Jewish engagement in the arts on campus, Weiss proposed a Jewish theater discussion group.</p>
<p>“Since junior year, I haven’t been acting in plays anymore, but I have been able to combine my connection with the theater community with my connection with the Jewish community, because I now have developed and led a Jewish theater discussion group through the Hillel,” she says, “We meet a few times throughout the semester and read a play or an excerpt from a play that deals with issues related to Jewish history, identity, politics, issues of assimilation — a whole range of topics.”</p>
<p>She curates the selection of plays and excerpts herself. Because some of the students involved in the discussion group have theater backgrounds, they sometimes act out the excerpts. For Weiss, leading the discussion group is “a fun way for me to get to be engaged in two communities at once.”</p>
<p><strong>Politically aware</strong></p>
<p>In her junior year, Weiss enrolled in Course 17.30 (Making Public Policy), a class in the political science department. “I just remember, I was always so excited to go to a 9:30 a.m. class, to an unusual extent, and to talk with [Professor Andrea Campbell] after class, and to do all of the assignments and to write the papers. That was definitely telling for me.”</p>
<p>“Political science was so totally engaging for me right away,” says Weiss. So much so, that Weiss decided to minor in it.</p>
<p>The summer before her senior year, Weiss interned at the MIT Washington Office. She reported on Congressional hearings by day and helped analyze how science impacted federal policymaking. The experience gave her a firsthand account of the divide between the scientific and political worlds, which she now hopes to address in the future.</p>
<p>“Scientific thinkers aren’t necessarily expected to consider moral and ideological and political questions in detail, and the same is true the other way around,” she says.</p>
<p>Weiss is optimistic that her experiences conducting research, leading discussions, and interacting with policymakers have given her the background necessary to tackle the issues she identified in Washington. She hopes to continue studying policy and political science after MIT, and wants to actively address the current disconnect between scientists and policymakers in her future work.</p>
<p>“I think that this cultural divide has to be addressed by not only by building relationships between policymakers and scientists, but also from the ground up, educating in a way that enables people to understand those who think differently than them,” she says.</p>
“I found diaries from 7th grade where I asked a whole stream of questions about the universe and the ‘edge of the universe’ and its expansion,” says senior Talia Weiss.
Photo: Ian MacLellan Profile, Students, Undergraduate, Undergraduate Research Opportunities Program (UROP), Urban studies and planning, STEM education, Political science, Policy, Physics, Theater, School of Science, SHASS, Laboratory for Nuclear ScienceArup Chakraborty elected to National Academy of Medicinehttp://news.mit.edu/2017/mit-professor-arup-chakraborty-elected-national-academy-medicine-1016
Recognized for his contributions to health, the distinguished professor is now a member of the national academies of medicine, science, and engineering.Mon, 16 Oct 2017 12:40:01 -0400Karen Baird | Institute for Medical Engineering and Sciencehttp://news.mit.edu/2017/mit-professor-arup-chakraborty-elected-national-academy-medicine-1016<p>Arup K. Chakraborty, the Robert T. Haslam Professor of Chemical Engineering&nbsp;and founding director of MIT’s Institute for Medical Engineering and Science (IMES), has been elected to the <a href="https://nam.edu" target="_blank">National Academy of Medicine</a> (NAM) in recognition of his distinguished contributions to medicine and health.</p>
<p>Chakraborty, a professor of physics, chemistry, and biological engineering,&nbsp;was&nbsp;one of 70 new members and 10 international members announced recently at the annual meeting of the academy. Membership in the NAM is considered one of the highest honors in the fields of health and medicine and recognizes individuals who have demonstrated outstanding professional achievements and commitment to service.&nbsp;</p>
<p>“I am honored to be elected to the National Academy of Medicine,” Chakraborty says.</p>
<p>As of this year’s elections, there are only 21 individuals in the United States who have achieved the trifeca of being&nbsp;members of the National Academy of Medicine, the <a href="http://www.nasonline.org" target="_blank">National Academy of Sciences</a>, and the <a href="https://www.nae.edu/" target="_blank">National Academy of Engineering</a>. Chakraborty joins fellow IMES core faculty members&nbsp;Jim Collins and Emery Brown&nbsp;and associate IMES member&nbsp;Robert Langer in&nbsp;sharing&nbsp;the distinction of being the only four members of the MIT faculty with membership in all three branches of the U.S. National Academies. He&nbsp;was elected a member of the National Academy of Sciences&nbsp;and the National Academy of Engineering&nbsp;for completely different bodies of work.</p>
<p>In addition to being the&nbsp;founding director of IMES, Chakraborty is also a founding steering committee member of the Ragon Institute of MIT, MGH, and Harvard&nbsp;and an associate member of the Broad Institute of MIT and Harvard. His research is focused&nbsp;at the intersection of various disciplines, in particular bringing immunology together with approaches from the physical and engineering sciences. His interests span T cell signaling, T cell development and repertoire, and a mechanistic understanding of HIV evolution, antibody evolution, and vaccine design.</p>
<p>Chakraborty’s work has been recognized with&nbsp;numerous other honors, including the NIH Director’s Pioneer Award, the E.O. Lawrence Medal for Life Sciences from the U.S. Department of Energy, the Allan P. Colburn and Professional Progress awards from the AIChE, a Dreyfus Teacher-Scholar award, and a National Young Investigator award. He is a fellow of the American Academy of Arts and Sciences and the American Association for the Advancement of Science, and serves on the U.S. Defense Science Board. He has also received four teaching awards.</p>
<p>The&nbsp;National Academy of Medicine, established in 1970 as the Institute of Medicine, is an independent organization of eminent professionals from diverse fields including health and medicine; the natural, social, and behavioral sciences; and beyond. It serves alongside the&nbsp;National Academy of Sciences&nbsp;and the&nbsp;National Academy of Engineering&nbsp;as an adviser to the nation and the international community. Through its domestic and global initiatives, the NAM works to address critical issues in health, medicine, and related policy and inspire positive action across sectors.&nbsp;The NAM collaborates closely with its peer academies and other divisions within the national academies.&nbsp;</p>
Arup K. Chakraborty, the Robert T. Haslam Professor of Chemical Engineering, professor of physics, chemistry, and biological engineering, and a core faculty member at the Institute for Medical Engineering and Science has been elected to the National Academy of Medicine in recognition of his distinguished contributions to medicine and health.Photo: Justin KnightSchool of Engineering, Awards, honors and fellowships, Biological engineering, Bioengineering and biotechnology, Broad Institute, Chemistry, Faculty, Health sciences and technology, Institute for Medical Engineering and Science (IMES), Physics3Q: Scott Hughes on cosmic distances and the future of gravitational wave astronomyhttp://news.mit.edu/2017/3q-scott-hughes-cosmic-distances-and-future-of-gravitational-wave-astronomy-1016
Professor of physics describes our understanding of the expansion of the universe through “standard sirens.”Mon, 16 Oct 2017 12:00:35 -0400Julia C. Keller | School of Sciencehttp://news.mit.edu/2017/3q-scott-hughes-cosmic-distances-and-future-of-gravitational-wave-astronomy-1016<p><em>On Monday, Oct. 16, National Science Foundation Director France Córdova, MIT senior research scientist and LIGO Scientific Collaboration spokesperson David Shoemaker, and other representatives from Caltech and the Virgo detector, announced the <a href="http://news.mit.edu/2017/ligo-virgo-first-detection-gravitational-waves-colliding-neutron-stars-1016" target="_self">detection of GW170817</a> — the merger of two neutron stars as observed by the two Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington.</em></p>
<p><em>Unlike the four <a href="http://news.mit.edu/2017/gravitational-waves-binary-black-hole-merger-observed-ligo-and-virgo-0927" target="_self">binary black hole systems previously detected</a>, the observation of a neutron-neutron star merger opens up a new chapter in the science of gravitational waves: the first correlation between gravitational waves (GWs) and an electromagnetic signal, in this case short-hard gamma ray bursts (SHBs).</em></p>
<p><em>In research preceding the LIGO detector systems’ first and second observing runs, Scott Hughes, MIT professor in the Department of Physics, working with Daniel Holz of the University of Chicago, developed a theoretical technique by which measuring the gravitational waves and SHBs of this kind of binary system could be used to measure cosmic distances, and to learn about the universe’s expansion.</em></p>
<p><em>Hughes, who is not a member of the LIGO collaboration, answers questions about this technique and the future of gravitational wave astronomy.</em></p>
<p><strong>Q: </strong>What are “standard candles” in astronomy and how does the “standard siren” technique allow us to measure cosmic distances with greater certainty than other methods?</p>
<p><strong>A:</strong> Measuring distances is one of the hardest problems in astronomy. What kind of yardstick can we use to measure distances so large that light takes millions or billions of years to travel across?</p>
<p>Imagine a gigantic lightbulb that puts out 400 trillion trillion watts — that’s the luminosity of our sun. The energy we receive from this lightbulb falls off as the distance squared between us and the bulb. Such a lightbulb 2 light years away would be four times dimmer than if it were 1 light year away. This source is a standard candle: an astronomical object whose luminosity is known so well that we can infer how far away it is from the brightness we measure.</p>
<p>Although nature doesn’t provide us with such standard lightbulbs, astronomers have found that certain objects have luminosities that can be calibrated so that they are effectively standardized. Key to standardizing these objects are a series of measurements called the “cosmic distance ladder.” This uses a technique called parallax, which examines how the relative position of nearby stars on the sky changes as the Earth moves in its orbit. Using parallax, astronomers have learned that a class of stars called Cepheid variables — thousands of times more luminous than our sun — are very good standard candles. They can find these candles in distant galaxies, and use them to determine how far away those galaxies are.</p>
<p>In 1986, Bernard Schutz of the University of Cardiff in Wales pointed out that binary coalescence — such as the merger of two neutron stars — is a self calibrating standard candle: Measuring its waves makes it possible to directly measure the binary’s distance without the cosmic distance ladder. Schutz’s key observation is that the rate at which the binary’s frequency changes is directly related to the system’s intrinsic gravitational wave “loudness.” (Gravitational waves have a sound-like character — recall the famous “chirp” from the first detection — and it is useful to think of strong events as loud, and weak events as quiet.)</p>
<p>Just as the observed brightness of a star depends on both its intrinsic luminosity and how far away it is, the strength of the gravitational waves that we measure depends on both their source’s intrinsic loudness and how far away it is. By observing the waves with detectors like LIGO and Virgo, we learn both the waves’ intrinsic loudness as well as their loudness at the Earth. This allows us to directly determine distance to the source.</p>
<p>About 12 years ago, Daniel Holz and I examined how well this idea could be implemented, focusing on how it could be done if the gravitational waves were accompanied by some electromagnetic signature, such as a short-hard gamma-ray burst. Given the sound-like character of gravitational waves, we named such an event a “standard siren.” Our analysis got us excited about how the self-calibrating nature of these events could make them powerful tools for important measurements in cosmology.</p>
<p><strong>Q:</strong> How does this observation provide a probe of the universe’s expansion and what could other potential observations — such as a black hole-neutron star merger — tell us about the origin of black holes or the expansion of our universe?</p>
<p><strong>A:</strong> Edwin Hubble first observed that our universe is expanding, finding that distant galaxies move away from us at a rate proportional to their distance. The wavelengths of light from such galaxies are shifted to the red part of the spectrum, a phenomenon in light akin to the Doppler effect in sound. Precise measurements of distance and redshift are needed in order to figure out how fast the expansion is proceeding. The binary inspiral of GW170817 measured its distance; telescope observations of the accompanying gamma-ray burst measured its redshift. Those are exactly the pieces of information needed to measure Hubble’s constant, which tells us how fast the universe is now expanding.</p>
<p>Any measurement of binary coalescence that is accompanied by an electromagnetic event, like a gamma-ray burst, can be used to measure the expansion of the universe exactly as was done with GW170817. Indeed, we hope for more events like this: Combining many distance-redshift measurements will make it possible to average out noise and other error effects, and improve our ability to measure Hubble’s constant.</p>
<p>Although Hubble’s constant had already been measured by a few different techniques, these techniques appear to be converging to two different values! It is unclear if this discrepancy is because of some currently unknown bit of cosmic physics, or if it is a systematic error in the measurements. Because the standard siren does not require a series of calibrations, it has tremendous promise for resolving this tension in the Hubble constant’s value.</p>
<p>In addition to telling us about the distance to the event, each of these measurements such as GW170817 provides a wealth of data about the masses and other properties of the objects involved. As we build up a catalog of data about things like black hole masses and spins and neutron star masses, we will gain more and deeper understanding of how these objects are distributed in the universe, shedding light on the nature of the matter that makes up neutron stars and how some of the heaviest elements were formed.</p>
<p><strong>Q:</strong> What might space-based gravitational wave and electromagnetic measurements tell us that ground-based measurements from LIGO or Virgo could not?</p>
<p><strong>A:</strong> This question is near to my heart, since I have spent a lot of my career thinking about measurements using the <a href="https://lisa.nasa.gov/" target="_blank">Laser Interferometer Space Antenna (LISA)</a> — the planned space-based gravitational-wave detector. Indeed, the primary focus of my first standard sirens paper with Holz was on sirens enabled by LISA measurements!</p>
<p>LISA will be sensitive to gravitational waves at much lower frequencies than LIGO and Virgo can measure. Low-frequency waves come from much more massive sources, like the coalescence of black holes millions of times more massive than the sun. Such sources may enable LISA to make standard siren measurements from sources that are tremendously far away — perhaps tens of billions of light years, from an epoch when the universe was relatively young.</p>
<p>The distant standard sirens that LISA may enable tell us about the expansion of the universe at a very different cosmic time than the relatively nearby sirens (a few hundred million light years away) that LIGO and Virgo measure. Together, these events would make it possible to precisely probe the expansion of the universe over a wide range of cosmic times, enabling a wholly new way of probing the large-scale geometry of our universe.</p>
Scott HughesPhoto: Department of PhysicsAstronomy, Astrophysics, Black holes, Kavli Institute, LIGO, Space, astronomy and planetary science, National Science Foundation (NSF), Research, Physics, School of Science, 3 Questions, FacultyLIGO and Virgo make first detection of gravitational waves produced by colliding neutron starshttp://news.mit.edu/2017/ligo-virgo-first-detection-gravitational-waves-colliding-neutron-stars-1016
Discovery marks first cosmic event observed in both gravitational waves and light.Mon, 16 Oct 2017 09:59:59 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/ligo-virgo-first-detection-gravitational-waves-colliding-neutron-stars-1016<p>For the first time, scientists have directly detected gravitational waves — ripples in space-time — in addition to light from the spectacular collision of two neutron stars. This marks the first time that a cosmic event has been viewed in both gravitational waves and light.</p>
<p>The discovery was made using the U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO); the Europe-based Virgo detector; and some 70 ground- and space-based observatories.</p>
<p>Neutron stars are the smallest, densest stars known to exist and are formed when massive stars explode in supernovas. As these neutron stars spiraled together, they emitted gravitational waves that were detectable for about 100 seconds; when they collided, a flash of light in the form of gamma rays was emitted and seen on Earth about two seconds after the gravitational waves. In the days and weeks following the smashup, other forms of light, or electromagnetic radiation — including X-ray, ultraviolet, optical, infrared, and radio waves — were detected.</p>
<p><iframe allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/sgkDoSbHHVU?rel=0" width="560"></iframe></p>
<p><span style="font-size:10px;"><em>Video: NASA's Goddard Space Flight Center/CI Lab</em></span></p>
<p>The observations have given astronomers an unprecedented opportunity to probe a collision of two neutron stars. For example, observations made by the U.S. Gemini Observatory, the European Very Large Telescope, and the Hubble Space Telescope reveal signatures of recently synthesized material, including gold and platinum, solving a decades-long mystery of where about half of all elements heavier than iron are produced.&nbsp;&nbsp;</p>
<p>The LIGO-Virgo results are published today in the journal <em>Physical Review Letters</em>; additional papers from the LIGO and Virgo collaborations and the astronomical community have been either submitted or accepted for publication in various journals.</p>
<p>“It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the universe,” says France A. Córdova, director of the National Science Foundation (NSF), which funds LIGO.&nbsp;“This discovery realizes a long-standing goal many of us have had, that is, to simultaneously observe rare cosmic events using both traditional as well as gravitational-wave observatories. Only through NSF’s four-decade investment in gravitational-wave observatories, coupled with telescopes that observe from radio to gamma-ray wavelengths, are we able to expand our opportunities to detect new cosmic phenomena and piece together a fresh narrative of the physics of stars in their death throes.”</p>
<p><iframe allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/F7-FSPyjc94?rel=0" width="560"></iframe></p>
<p><span style="font-size:10px;"><em>Video: Georgia Tech</em></span></p>
<p><strong>A stellar sign</strong></p>
<p>The gravitational signal, named GW170817, was first detected on Aug. 17 at 8:41 a.m. Eastern Daylight Time; the detection was made by the two identical LIGO detectors, located in Hanford, Washington, and Livingston, Louisiana. The information provided by the third detector, Virgo, situated near Pisa, Italy, enabled an improvement in localizing the cosmic event. At the time, LIGO was nearing the end of its second observing run since being upgraded in a program called Advanced LIGO, while Virgo had begun its first run after recently completing an upgrade known as Advanced Virgo.</p>
<p>The NSF-funded LIGO observatories were conceived, constructed, and operated by Caltech and MIT. Virgo is funded by the Istituto Nazionale di Fisica Nucleare (INFN) in Italy and the Centre National de la Recherche Scientifique (CNRS) in France, and operated by the European Gravitational Observatory. Some 1,500 scientists in the LIGO Scientific Collaboration and the Virgo Collaboration work together to operate the detectors and to process and understand the gravitational-wave data they capture.</p>
<p>Each observatory consists of two long tunnels arranged in an L shape, at the joint of which a laser beam is split in two. Light is sent down the length of each tunnel, then reflected back in the direction it came from by a suspended mirror. In the absence of gravitational waves, the laser light in each tunnel should return to the location where the beams were split, at precisely the same time. If a gravitational wave passes through the observatory, it will alter each laser beam’s arrival time, creating an almost imperceptible change in the observatory’s output signal.</p>
<p>On Aug. 17, LIGO’s real-time data analysis software caught a strong signal of gravitational waves from space in one of the two LIGO detectors. At nearly the same time, the Gamma-ray Burst Monitor on NASA’s Fermi space telescope had detected a burst of gamma rays. LIGO-Virgo analysis software put the two signals together and saw it was highly unlikely to be a chance coincidence, and another automated LIGO analysis indicated that there was a coincident gravitational wave signal in the other LIGO detector. Rapid gravitational-wave detection by the LIGO-Virgo team, coupled with Fermi’s gamma-ray detection, enabled the launch of follow-up by telescopes around the world.</p>
<p>The LIGO data indicated that two astrophysical objects located at the relatively close distance of about 130 million light years from Earth had been spiraling in toward each other. It appeared that the objects were not as massive as binary black holes — objects that LIGO and Virgo have previously detected. Instead, the inspiraling objects were estimated to be in a range from around 1.1 to 1.6 times the mass of the sun, in the mass range of neutron stars. A neutron star is about 20 kilometers, or 12 miles, in diameter and is so dense that a teaspoon of neutron star material has a mass of about a billion tons.</p>
<p>While binary black holes produce “chirps” lasting a fraction of a second in the LIGO detector’s sensitive band, the Aug. 17 chirp lasted approximately 100 seconds and was seen through the entire frequency range of LIGO — about the same range as common musical instruments. Scientists could identify the chirp source as objects that were much less massive than the black holes seen to date.</p>
<p>“It immediately appeared to us the source was likely to be neutron stars, the other coveted source we were hoping to see — and promising the world we would see,” says David Shoemaker, spokesperson for the LIGO Scientific Collaboration and senior research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “From informing detailed models of the inner workings of neutron stars and the emissions they produce, to more fundamental physics such as general relativity, this event is just so rich. It is a gift that will keep on giving.”</p>
<p>“Our background analysis showed an event of this strength happens less than once in 80,000 years by random coincidence, so we recognized this right away as a very confident detection and a remarkably nearby source,” adds Laura Cadonati, professor of physics at Georgia Tech and deputy spokesperson for the LIGO Scientific Collaboration. “This detection has genuinely opened the doors to a new way of doing astrophysics. I expect it will be remembered as one of the most studied astrophysical events in history.”</p>
<p>Theorists have predicted that when neutron stars collide, they should give off gravitational waves and gamma rays, along with powerful jets that emit light across the electromagnetic spectrum. The gamma-ray burst detected by Fermi, and soon thereafter confirmed by the European Space Agency’s gamma-ray observatory INTEGRAL, is what’s called a short gamma-ray burst; the new observations confirm that at least some short gamma-ray bursts are generated by the merging of neutron stars — something that was only theorized before.</p>
<p>“For decades we’ve suspected short gamma-ray bursts were powered by neutron star mergers,” says Fermi Project Scientist Julie McEnery of NASA’s Goddard Space Flight Center. “Now, with the incredible data from LIGO and Virgo for this event, we have the answer. The gravitational waves tell us that the merging objects had masses consistent with neutron stars, and the flash of gamma rays tells us that the objects are unlikely to be black holes, since a collision of black holes is not expected to give off light."</p>
<p>But while one mystery appears to be solved, new mysteries have emerged. The observed short gamma-ray burst was one of the closest to Earth seen so far, yet it was surprisingly weak for its distance. Scientists are beginning to propose models for why this might be, McEnery says, adding that new insights are likely to arise for years to come.</p>
<p><strong>A patch in the sky</strong></p>
<p>Though the LIGO detectors first picked up the gravitational wave in the United States, Virgo, in Italy, played a key role in the story. Due to its orientation with respect to the source at the time of detection, Virgo recovered a small signal; combined with the signal sizes and timing in the LIGO detectors, this allowed scientists&nbsp;to precisely triangulate the position in the sky. After performing a thorough vetting to make sure the signals were not an artifact of instrumentation, scientists concluded that a gravitational wave came from a relatively small patch in the southern sky.</p>
<p>“This event has the most precise sky localization of all detected gravitational waves so far,” says Jo van den Brand of Nikhef (the Dutch National Institute for Subatomic Physics) and VU University Amsterdam, who is the spokesperson for the Virgo collaboration. “This record precision enabled astronomers to perform follow-up observations that led to a plethora of breathtaking results.”</p>
<p>“This result is a great example of the effectiveness of teamwork, of the importance of coordinating, and of the value of scientific collaboration,” adds EGO Director Federico Ferrini. “We are delighted to have played our relevant part in this extraordinary scientific challenge: Without Virgo, it would have been very difficult to locate the source of the gravitational waves.”</p>
<p>Fermi was able to provide a localization that was later confirmed and greatly refined with the coordinates provided by the combined LIGO-Virgo detection. With these coordinates, a handful of observatories around the world were able, hours later, to start searching the region of the sky where the signal was thought to originate. A new point of light, resembling a new star, was first found by optical telescopes. Ultimately, about 70 observatories on the ground and in space observed the event at their representative wavelengths.</p>
<p>“This detection opens the window of a long-awaited ‘multimessenger’ astronomy,” says Caltech’s David H. Reitze, executive director of the LIGO Laboratory. “It’s the first time that we’ve observed a cataclysmic astrophysical event in both gravitational waves and electromagnetic waves — our cosmic messengers. Gravitational-wave astronomy offers new opportunities to understand the properties of neutron stars in ways that just can’t be achieved with electromagnetic astronomy alone.”</p>
<p><strong>A fireball and an afterglow</strong></p>
<p>Each electromagnetic observatory will be releasing its own detailed observations of the astrophysical event. In the meantime, a general picture is emerging among all observatories involved that further confirms that the initial gravitational-wave signal indeed came from a pair of inspiraling neutron stars.</p>
<p>Approximately 130 million years ago, the two neutron stars were in their final moments of orbiting each other, separated only by about 300 kilometers, or 200 miles, and gathering speed while closing the distance between them. As the stars spiraled faster and closer together, they stretched and distorted the surrounding space-time, giving off energy in the form of powerful gravitational waves, before smashing into each other.</p>
<p>At the moment of collision, the bulk of the two neutron stars merged into one ultradense object, emitting a “fireball” of gamma rays. The initial gamma-ray measurements, combined with the gravitational-wave detection, also provide confirmation for Einstein’s general theory of relativity, which predicts that gravitational waves should travel at the speed of light.</p>
<p>Theorists have predicted that what follows the initial fireball is a “kilonova” — a phenomenon by which the material that is left over from the neutron star collision, which glows with light, is blown out of the immediate region and far out into space. The new light-based observations show that heavy elements, such as lead and gold, are created in these collisions and subsequently distributed throughout the universe.</p>
<p>In the weeks and months ahead, telescopes around the world will continue to observe the afterglow of the neutron star merger and gather further evidence about various stages of the merger, its interaction with its surroundings, and the processes that produce the heaviest elements in the universe.</p>
<p>“When we were first planning LIGO back in the late 1980s, we knew that we would ultimately need an international network of gravitational-wave observatories, including Europe, to help localize the gravitational-wave sources so that light-based telescopes can follow up and study the glow of events like this neutron star merger,” says Caltech’s Fred Raab, LIGO associate director for observatory operations. “Today we can say that our gravitational-wave network is working together brilliantly with the light-based observatories to usher in a new era in astronomy, and will improve with the planned addition of observatories in Japan and India.”</p>
<p>LIGO is funded by the<a href="http://www.nsf.gov/">&nbsp;NSF</a>, and operated by&nbsp;<a href="http://www.ligo.caltech.edu/">Caltech</a>&nbsp;and&nbsp;<a href="http://space.mit.edu/LIGO/">MIT</a>, which conceived of LIGO and led the Initial and Advanced LIGO projects.&nbsp;Financial support for the Advanced LIGO project was led by the NSF with Germany (<a href="http://www.mpg.de/en">Max Planck Society</a>), the U.K. (<a href="http://www.stfc.ac.uk/">Science and Technology Facilities Council</a>) and Australia (<a href="http://www.arc.gov.au/">Australian Research Council</a>) making significant commitments and contributions to the project.</p>
<p>More than 1,200 scientists&nbsp;and some 100 <a href="https://my.ligo.org/census.php">institutions</a> from around the world participate in the effort through the <a href="http://ligo.org/">LIGO Scientific Collaboration</a>, which includes the GEO Collaboration and the Australian collaboration OzGrav. Additional partners are listed at&nbsp;<a href="http://ligo.org/partners.php">ligo.org/partners.php</a>.&nbsp;</p>
<p>The Virgo collaboration consists of more than 280 physicists and engineers belonging to 20 different European research groups: six from <a href="http://www.cnrs.fr/">Centre National de la Recherche Scientifique</a> (CNRS) in France; eight from the <a href="http://home.infn.it/it/">Istituto Nazionale di Fisica Nucleare</a> (INFN) in Italy; two in the Netherlands with <a href="https://www.nikhef.nl/en/">Nikhef</a>; the MTA Wigner RCP in Hungary; the POLGRAW group in Poland; the University of Valencia in Spain; and the European Gravitational Observatory,&nbsp;EGO, the laboratory hosting the Virgo detector near Pisa in Italy, funded by CNRS, INFN, and Nikhef.</p>
Artist’s illustration of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays that are shot out just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars are also depicted. The clouds glow with visible and other wavelengths of light.
Image: National Science Foundation/LIGO/Sonoma State University/A. SimonnetAstronomy, Astrophysics, Physics, Kavli Institute, LIGO, National Science Foundation (NSF), School of Science, Space, astronomy and planetary scienceGrad students earn Department of Energy computational fellowshipshttp://news.mit.edu/2017/four-mit-graduate-students-awarded-department-energy-computational-fellowships-1011
Ahrens, Rathbun, Silmore, and Wei are recognized for tackling complex science and engineering problems of national importance.Wed, 11 Oct 2017 16:40:01 -0400Melanie Miller Kaufman | Department of Chemical Engineeringhttp://news.mit.edu/2017/four-mit-graduate-students-awarded-department-energy-computational-fellowships-1011<p>Four first-year graduate students have been awarded U.S. Department of Energy (DOE) Computational Science Graduate Fellowships to support their research. Fellows&nbsp;receive full tuition and fees plus an annual stipend and academic allowance, renewable for up to four years. Less than 5 percent of applicants are chosen for the fellowship each year.</p>
<p>The computational science fellowship program is&nbsp;administered by the Krell Institute and funded by the DOE’s Office of Science and the National Nuclear Security Administration. Each year, the program grants fellowships to support doctoral students who focus on using high-performance computers to solve complex science and engineering problems of national importance. Recipients must complete courses in a scientific or engineering discipline, plus computer science and applied mathematics. They also must do a three-month research practicum at one of 21 DOE laboratories or sites across the country.</p>
<p>Four MIT students were awarded&nbsp;DOE Computational Science Graduate Fellowships&nbsp;for 2017.</p>
<p><a href="https://www.csail.mit.edu/user/4820" target="_blank">Peter J. Ahrens</a> is&nbsp;a graduate student in the Department of Electrical Engineering and Computer Science, and his&nbsp;research focuses on using computer science to improve numerical software for scientists. Writing performance engineered code is difficult because one must optimize for each combination of numerical operation, scientific application, and available hardware, so Ahrens creates algorithms and software which can programmatically generate optimized code for each use case. He also uses code generation within the Julia programming language to write novel interfaces that make it easier to use numerical software.</p>
<p><a href="https://odge.mit.edu/undergraduate/msrp/2015-msrp-interns/miriam-rathbun/" target="_blank">Miriam Rathbun</a> is a graduate student in the Department of Nuclear Science and Engineering and&nbsp;a member of Benoit Forget’s research group. Rathbun’s computational reactor physics research focuses on high-fidelity modeling of nuclear reactors. In particular, she is interested in multiphysics problems where several physical phenomena influence each other. Multiphysics research seeks to create a platform for solvers to be more compatible with each other and to make simulations that more accurately predict reality.</p>
<p><a href="https://srg.mit.edu/kevin-silmore" target="_blank">Kevin Silmore</a>&nbsp;of the Department of Chemical Engineering&nbsp;studies the dynamics and self-assembly of anisotropic colloidal particles, or particles that are not spherical. There are countless examples of particles that either occur in nature or are engineered in the laboratory that are not spherical. One prime example is carbon nanotubes, which exhibit many interesting properties and can be used in applications ranging from biosensors to energy harvesters. A better understanding of the physical processes that govern the behavior of such particles could therefore help inform the design of advanced materials with tunable electronic, optical, or mechanical properties.</p>
<p>Annie Yuan Wei, a student in the Department of Physics, intends to work in quantum information quantum algorithms, and quantum computing. Her research&nbsp;involves thinking about how quantum mechanics relates to information processing&nbsp;and how researchers can come up with ways to do things with quantum computers that might not be possible today.</p>
<p>Since it was launched in 1991, the fellowship program&nbsp;has supported 436 students at more than 65 universities. These students are among&nbsp;20 first-year recipients, bringing the total number of current fellows to 79&nbsp;in 14 states.</p>
<p>For more information on the DOE Computational Science Graduate Fellowships, please visit the <a href="http://www.krellinst.org/csgf" target="_blank">Krell Institute website</a>.</p>
The 2017 MIT recipients of the U.S. Department of Energy Computational Science Graduate Fellowships are (clockwise from top left) Peter Ahrens, Miriam Rathbun, Annie Yuan Wei, and Kevin Silmore.Image courtesy of the Department of Chemical Engineering.School of Engineering, Chemical engineering, Awards, honors and fellowships, Computer modeling, Department of Energy (DoE), Electrical Engineering & Computer Science (eecs), Graduate, postdoctoral, Nuclear science and engineering, Nuclear power and reactors, Quantum computing, Physics, Research, StudentsEngineers identify key to albatross’ marathon flighthttp://news.mit.edu/2017/engineers-identify-key-albatross-marathon-flight-1011
Flying in shallow arcs helps birds stay aloft with less effort.Tue, 10 Oct 2017 23:59:59 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/engineers-identify-key-albatross-marathon-flight-1011<p>The albatross is one of the most efficient travelers in the animal world. One species, the wandering albatross, can fly nearly 500 miles in a single day, with just an occasional flap of its wings. The birds use their formidable wingspans, measuring up to 11 feet across, to catch and ride the wind.</p>
<p>Observers have noted for centuries that these feathered giants keep themselves aloft for hours, just above the ocean surface, by soaring and diving between contrasting currents of air, as if riding a sidewinding rollercoaster — a flight pattern known as dynamic soaring.</p>
<p>Now engineers at MIT have developed a new model to simulate dynamic soaring, and have used it to identify the optimal flight pattern that an albatross should take in order to harvest the most wind and energy. They found that as an albatross banks or turns to dive down and soar up, it should do so in shallow arcs, keeping almost to a straight, forward trajectory.</p>
<p>The new model, they say, will be useful in gauging how albatross flight patterns may change as wind patterns shift with changing climate. It also may inform the design of wind-propelled drones and gliders which, if programmed with energy-efficient trajectories for given wind conditions, could be used to perform long-duration, long-range monitoring missions in remote regions of the world.</p>
<p>“The wandering albatross lives in the Southern Ocean, which is not very well-known. It’s very hard to get there, and there is a lot of wind and waves,” says Gabriel Bousquet, a graduate student in MIT’s Department of Mechanical Engineering. “The region is extremely important for understanding the dynamics of climate change. With robots that can use the wind, you could monitor in real-time and get much denser data than we can now. This is an important step forward to actually write algorithms for robots to be able to use the wind.”</p>
<p>Bousquet is the first author of a paper reporting the team’s results, published in the journal <em>Interface</em>. His co-authors are Jean-Jacques Slotine, professor of mechanical engineering and information sciences and of brain and cognitive sciences, and Michael Triantafyllou, the Henry L. and Grace Doherty Professor in Ocean Science and Engineering, and professor of mechanical and ocean engineering.</p>
<p><strong>Competitve soaring</strong></p>
<p>The team’s project was inspired, in part, by contests of dynamic soaring, in which competitors launch gliders from atop mountains and track the speed of each glider as it dives down, soars up, then doubles back and dives down again in a loop, propelled by the winds.</p>
<p>“These planes, without any engines, can go over 500 miles per hour, in a loop,” Triantafyllou says. “It sounds strange — how can you keep pumping energy out of what looks like nothing?”</p>
<p>It turns out the gliders are given a boost by varying wind currents. When a glider is launched from atop a mountain, high winds can act as a thruster, speeding the glider along until it reaches a sheltered layer of slower winds, whereupon it may reorient its flight direction before climbing back upward to the region of high winds.</p>
<p>The same wind-propelled phenomenon plays out in the flight of the albatross, Bousquet says, the only major difference being that, rather than lofting down behind a mountain, an albatross soars over water<s>. </s></p>
<p>“The question we looked at was, since the wind is fast high above the water, and slow near the surface, how can we take advantage of these inhomogeneities and exploit wind energy in order to fly in an efficient way?” Bousquet says.</p>
<p><strong>Riding the wind</strong></p>
<p>Renowned English physicist Lord Rayleigh was the first to describe dynamic soaring in mathematical modeling terms, predicting that albatrosses should fly in a series of arcing, 180-degree half-circles as they alternately soar through layers of high wind and swoop down to layers of low wind. This has been the general understanding, even today.</p>
<p>However, Bousquet and his colleagues came to a quite different conclusion. The team first modeled the wind field, drawing up a relatively simple equation to represent the change in wind speed with altitude. They specifically noted the thickness of the shear layer, which can be thought of as the distance between a layer of slow winds and a layer of fast winds.</p>
<p>They then used a three-dimensional model to represent the flight of an albatross or glider. This model consists of complicated equations of motion that are extremely difficult to solve, as they account for interactions within and between multiple layers of the atmosphere. The researchers solved those complicated equations using a method called numerical optimization. They varied the thickness of the shear layer and looked for the minimum wind needed to sustain flight. They found that the thinner the shear layer, the less wind was needed to keep a bird aloft. In other words, the closer the layers of slow and fast winds, the less energy an albatross must expend to stay in the air.</p>
<p>As an albatross only flies within the first 5 to 20 meters above the water, the researchers managed to simplify the model. They rewrote the equations, essentially compressing them into a two-dimensional model, in a way that still accurately simulates the flight of an albatross or glider.</p>
<p>They also found, both in the numerical and two-dimensional models, that as the shear layer thins, a bird can fly more efficiently if it dives and soars between wind layers in shallow arcs rather than wide half-circles. Bousquet says this may at first seem counterintuitive.</p>
<p>“One way to look at it is that, at each crossing between the slow and fast layers, some airspeed is gained,” Bousquet explains.&nbsp;“The most airspeed in a single crossing is gained if crossing directly up- or downwind — that’s what happens with half-turns. However, there is also an airspeed loss due to drag while turning. So it turns out that the important metric is the ratio between gains and losses. So it is more efficient to gain a little, often, as is the case with small turns, rather than a lot, but rarely, such as with half turns.”</p>
<p>The team computed that the most energy-efficient flight trajectory would be to fly in extremely shallow arcs, approaching zero degrees in amplitude. To see whether these results held up in the real world, they compared their predictions with actual GPS recordings taken of albatrosses in flight. These recordings revealed that the birds tended to turn by an average angle of 60 degrees, far shallower an arc than the 180-degree half-circle that most scientists have assumed the animals follow.</p>
<p>Slotine says the paper’s insights can serve as a map for building wind-powered drones and gliders — a goal that the team is actively working toward.</p>
<p>“If we want to design robots that use the wind, now we know that moving forward along shallow arcs favors both&nbsp;travel speed and efficient energy extraction,” Slotine says. “And it turns out the albatrosses are doing it that way.”</p>
<p>This research was funded, in part, by a Fulbright Science and Technology fellowship, a Professor Amar G. Bose research grant, a Link Foundation Ocean Engineering and Instrumentation fellowship, and by the the Singapore-MIT Alliance for Research and Technology.</p>
Engineers at MIT have developed a new model to simulate dynamic soaring, and have used it to identify the optimal flight pattern that an albatross should take in order to harvest the most wind and energy. They found that as an albatross banks or turns, it should do so in shallow arcs, keeping almost to a straight, forward trajectory.
Biology, Computer modeling, Drones, Energy, Fluid dynamics, Mechanical engineering, Physics, Research, Robots, School of Engineering, Wind, Animals, Biomimetics, BioinspirationSchool of Science welcomes new faculty membershttp://news.mit.edu/2017/mit-school-of-science-welcomes-new-faculty-members-1010
This fall brings 14 new professors in the departments of Biology, Chemistry, Mathematics, and Physics.Tue, 10 Oct 2017 17:15:01 -0400School of Sciencehttp://news.mit.edu/2017/mit-school-of-science-welcomes-new-faculty-members-1010<p>This fall, the MIT School of Science has welcomed&nbsp;14 new professors in the departments of Biology, Chemistry, Mathematics, and Physics.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/crossfield_ian.html" target="_blank">Ian J. M. Crossfield</a> focuses on the atmospheric characterization of exoplanets through all possible methods — transits, eclipses, phase curves, and direct imaging — from the ground and from space, with an additional interest in the discovery of new exoplanets, especially those whose atmospheres that can be studied in more detail. He joins the MIT Department of Physics as an assistant professor.</p>
<p><a href="https://biology.mit.edu/people/jhdavis" target="_blank">Joey Davis</a>, an assistant professor in the Department of Biology, studies the molecular mechanisms underpinning autophagy using biochemical, biophysical, and structural biology techniques such as mass spectrometry and cryo-electron microscopy. This pathway is responsible for protein and organelle degradation and has been linked to a variety of aging associated disorders including neurodegeneration and cancer.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/harlow_daniel.html" target="_blank">Daniel Harlow</a> works on black holes and cosmology, viewed through the lens of quantum gravity and quantum field theory. He has joined&nbsp;the Department of Physics as assistant professor.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/harris_philip.html" target="_blank">Philip Harris</a>, a new assistant professor in the&nbsp;Department of Physics, searches for dark matter, seeking a deeper understanding of the petabytes of data collected at the Large Hadron Collider. Much of his research exploits new techniques to resolve the structure of quark and gluon decays, known as jet substructure.</p>
<p><a href="http://web.mit.edu/physics/people/faculty/hen_or.html" target="_blank">Or Hen</a> studies quantum chromodynamics effects in the nuclear medium, and the interplay between partonic and nucleonic degrees of freedom in nuclei, conducting experiments at the Thomas Jefferson and Fermi National Accelerator Laboratories, as well as other accelerators around the world. He has joined the faculty as an assistant professor in the Department of Physics and the Laboratory of Nuclear Science.</p>
<p><a href="http://chemistry.mit.edu/people/kiessling-laura" target="_blank">Laura Kiessling</a> investigates how carbohydrates are assembled, recognized, and function in living cells, which is crucial to understanding key biological processes such as bacterial cell wall biogenesis, bacteria chemotaxis, enzyme catalysis and inhibition, immunity, and stem cell propagation and differentiation. She is&nbsp;the new Novartis Professor of Chemistry.</p>
<p><a href="https://biology.mit.edu/people/rlamason" target="_blank">Rebecca Lamason</a> investigates how intracellular bacterial pathogens hijack host cell processes to promote infection. In particular, she studies how <em>Rickettsia parkeri</em> and <em>Listeria monocytogenes</em> move through tissues via a process called cell-to-cell spread. She has joined&nbsp;the Department of Biology as an assistant professor.</p>
<p><a href="https://biology.mit.edu/people/sebastian_lourido" target="_blank">Sebastian Lourido</a> studies the molecular events that enable parasites in the phylum Apicomplexa to remain widespread and deadly infectious agents. Lourido uses <em>Toxoplasma gondii </em>to model processes conserved throughout the phylum, in order to expand our understanding of eukaryotic diversity and identify specific features that can be targeted to treat parasite infections. He has been welcomed into the&nbsp;Department of Biology as an assistant professor.</p>
<p><a href="http://chemistry.mit.edu/people/raines-ronald" target="_blank">Ronald T. Raines</a>, who has joined&nbsp;the faculty as the Firmenich Professor of Chemistry, uses techniques that range from synthetic chemistry to cell biology to illuminate in atomic detail both the chemical basis and the biological purpose for protein structure and protein function. He seeks insights into the relationship between amino-acid sequence and protein function (or dysfunction), as well as to the creation of novel proteins with desirable properties.</p>
<p><a href="https://math.mit.edu/directory/profile.php?pid=2007" target="_blank">Giulia Saccà</a> is an algebraic geometer with a focus on hyperkähler and Calabi-Yau manifolds, K3 surfaces, moduli spaces of sheaves, families of abelian varieties and their degenerations, and symplectic resolutions. She is now an assistant professor in the&nbsp;Department of Mathematics.</p>
<p><a href="https://biology.mit.edu/people/stefani_spranger" target="_blank">Stefani Spranger</a> studies the interactions between cancer and the immune system, with the goal of improving existing immunotherapies or developing novel therapeutic approaches. Spranger seeks to understand how CD8 T cells, otherwise known as killer&nbsp;T cells, are excluded from the tumor microenvironment, with a focus on lung and pancreatic cancers. She has joined&nbsp;the Department of Biology as an assistant professor.</p>
<p><a href="http://chemistry.mit.edu/people/suess-daniel" target="_blank">Daniel Suess</a> works at the intersection of inorganic and biological chemistry, studying redox reactions that underpin global biogeochemical cycles, metabolism, and energy conversion. He develops chemical strategies for attaining precise, molecular-level control over the structures of complex active sites. In doing so, his research yields detailed mechanistic insight and enables the preparation of catalysts with improved function. Suess is an assistant professor in&nbsp;the Department of Chemistry.</p>
<p><a href="https://math.mit.edu/directory/profile.php?pid=1998" target="_blank">Wei Zhang</a> is a number theorist who works in arithmetic geometry, with special interest in fundamental objects such as L-functions, which appear in the Riemann hypothesis and its generalizations, and are central to the Langlands program. Zhang has joined&nbsp;the Department of Mathematics as a full professor.</p>
<p><a href="http://math.mit.edu/directory/profile.php?pid=1354" target="_blank">Yufei Zhao</a>, who has joined&nbsp;the Department of Mathematics as an assistant professor,<strong>&nbsp;</strong>works in combinatorics and graph theory, and is especially interested in problems with extremal, probabilistic, and additive flavors.</p>
This fall's additions for the School of Science faculty: (top, l-r) Ian Crossfield, Joey Davis, Daniel Harlow, Philip Harris, Or Hen; (middle, l-r): Laura Kiessling, Rebecca Lamason, Sebastian Lourido, Ronald Raines; (bottom, l-r): Giulia Saccà, Stefani Spranger, Daniel Suess, Wei Zhang, and Yufei Zhao.Image courtesy of the School of ScienceSchool of Science, Biology, Chemistry, Mathematics, Physics, FacultyIntroducing the Materials Research Laboratory at MIThttp://news.mit.edu/2017/introducing-mit-materials-research-laboratory-mrl-1010
Materials Processing Center, Center for Materials Science and Engineering merger brings together formidable resources for advancing next-generation materials.Tue, 10 Oct 2017 12:40:01 -0400Denis Paiste | Materials Research Laboratoryhttp://news.mit.edu/2017/introducing-mit-materials-research-laboratory-mrl-1010<p>The Materials Processing Center (MPC) and the Center for Materials Science and Engineering (CMSE), which together serve more than 150 MIT engineering and science researchers, announced today their merger as the MIT Materials Research Laboratory.</p>
<p>The MIT Materials Research Laboratory (MRL) encompasses research on energy conversion and storage; quantum materials; spintronics; photonics; metals; integrated microsystems; materials sustainability; solid-state ionics; complex oxide electronic properties; biogels; and functional fibers. “These are all interdisciplinary topics in which materials play a critical role,” says MRL Director Carl V. Thompson, who is the Stavros Salapatas Professor of Materials Science and Engineering at MIT. “The focus is on scientific discovery and how to design and make materials that lead to systems that have improved performance or that enable new approaches to existing problems.”</p>
<p>The partnership joins the Materials Processing Center’s wide diversity of materials research, funded by industry, foundations, and government agencies; and the Center for Materials Science and Engineering’s basic science, educational outreach, and shared experimental facilities that are funded under the National Science Foundation Materials Research Science and Engineering Center (MRSEC) program. Combined research volume was $21.5 million for the fiscal year ended on June 30.</p>
<p>“The merger of these two successful centers will streamline the organization of materials research on campus in a manner that will enhance the ability for effective collaboration,” notes <a href="http://research.mit.edu/about-office-vice-president-research" target="_blank">Maria Zuber</a>, MIT vice president for research and the E. A. Griswold Professor of Geophysics. The new center will report to Zuber.</p>
<p>Associate professor of materials science and engineering Geoffrey S.D. Beach has been appointed as co-director of the MRL and principal investigator for the MRSEC, succeeding TDK Professor of Polymer Materials Science and Engineering Michael F. Rubner, who is retiring after 16 years as CMSE director.<br />
<br />
Both an external advisory board, whose members come from industry, government, and academia, and an internal advisory board, made up of MIT faculty, will guide the MRL. “The formation of the Materials Research Laboratory is very exciting,” says Julia M. Phillips, chair of the MRL External Advisory Board and executive emerita at Sandia National Laboratories. “The MPC and CMSE have each been pillars of MIT’s outstanding materials community for many years. Bringing them together will take them to the next level of collaboration, combining outstanding research with important tools and capabilities to provide a critical connection to MIT.nano as well as a common and enhanced interface between materials at MIT and its industrial partners and academic collaborators.”</p>
<p>The MIT MRL will work hand-in-hand with&nbsp;<a dir="ltr" href="https://mitnano.mit.edu" rel="noopener noreferrer" target="_blank">MIT.nano</a>, the central research facility being built in the heart of the MIT campus due to open in June 2018. “We look forward to working with them not only as an important partner, but as a good next door neighbor,” Thompson says.</p>
<p><strong>Groundbreaking research</strong></p>
<p>The MRL will benefit from the long history of research breakthroughs under CMSE and MPC such as “<a dir="ltr" href="http://news.mit.edu/1998/mirror-1209" rel="noopener noreferrer" target="_self">perfect mirror</a>” technology in 1998 that led to a new kind of fiber optic surgery and a spinout company; <a dir="ltr" href="http://www.omni-guide.com" rel="noopener noreferrer" target="_blank">OmniGuide Surgical</a>; and the first germanium laser operating at room temperature in 2012. “Research breakthroughs by their very nature are hard to predict, but what we can do is we can create an environment that leads to research breakthroughs,” Thompson says. “The successful model in both MPC and CMSE is to bring together people interested in materials, but with different disciplinary backgrounds. We’ve done that separately, we’ll do it together, and the expectation is that we’ll do it even more effectively.”</p>
<p>MRL supports campus-based work by MIT faculty in three U.S. <a href="http://www.manufacturingusa.com/institutes" target="_blank">Manufacturing Innovation Institutes</a>, with a fourth likely in the area of materials sustainability. Current initiatives include the Lightweight Innovations for Tomorrow, the American Institute for Manufacturing Integrated Photonics, and the Advanced Functional Fibers of America, as well as oxide-based fuel cell‬ materials and higher efficiency ‬‬solar cells. ‬‬‬‬‬‬</p>
<p>The annual Materials Day Symposium and Poster Session will be held Wednesday, Oct. 11, 8 a.m. to 6 p.m., in Kresge Auditorium (Building W16) and the Stratton Student Center (Building W20). The theme will be “Frontiers in Materials Research.”&nbsp;In addition to MIT faculty research presentations, there will be a panel discussion featuring senior leaders of MIT’s materials research community. The poster session includes students and postdocs from multiple fields who collaborate on materials-related research.</p>
<p><strong>Mixing old and new</strong></p>
<p>While condensed-matter physicists are pursuing the latest research in exotic states of two-dimensional materials such as magnetically and optically driven topological semimetals, research in metallurgy, the historic foundation for materials science, is also undergoing a revival. For example, Department of Materials Science and Engineering head Christopher A. Schuh developed&nbsp;<a dir="ltr" href="http://news.mit.edu/2014/faculty-highlight-christopher-schuh-1030" rel="noopener noreferrer" target="_self">nanostructured metal alloys</a>&nbsp;and John F. Elliott Professor of Materials Chemistry Donald R. Sadoway pioneered a novel&nbsp;<a dir="ltr" href="http://news.mit.edu/2016/battery-molten-metals-0112" rel="noopener noreferrer" target="_self">molten-metal battery</a>&nbsp;for grid-level energy storage. “The excellent support from MPC staff over the years has allowed me to get the most from my funding. For me, CMSE has been critical for its superb central user facilities,” Sadoway says. “The merger of these two represents a major consolidation for materials researchers at MIT. I look forward to what comes next.”</p>
<p>Interdisciplinary research groups, which bring faculty from different disciplines together, are a key feature of the MRSEC. At the heart of each group is a set of fundamental hypotheses aimed at resolving key scientific questions about an important emerging area of materials science. Past projects have focused on quantum dots, battery materials, functional fibers, integrated silicon photonics, and many other topics. MRSEC-funded research generated approximately 1,100 new jobs through spinouts such as&nbsp;<a dir="ltr" href="http://www.amsc.com" rel="noopener noreferrer" target="_blank">American Superconductor</a>,&nbsp;<a dir="ltr" href="http://www.omni-guide.com" rel="noopener noreferrer" target="_blank">OmniGuide Surgical Surgical</a>,&nbsp;<a dir="ltr" href="https://www.displaysupplychain.com/blog/-samsung-buys-qd-visions-ip-for-70m-and-the-future-of-quantum-dots" rel="noopener noreferrer" target="_blank">QD Vision</a>, and&nbsp;<a dir="ltr" href="http://www.luminus.com/index.html" rel="noopener noreferrer" target="_blank">Luminus Devices</a>.</p>
<p>“Our greatest legacy is bringing people together to produce fundamental new science, and then allowing those researchers to explore that new science in ways that may be beneficial to society, as well as to develop new technologies and launch companies,” Rubner says.</p>
<p>New MRL co-director Beach’s research explores complex nanoscale structures in which interactions between different materials — metals and oxides, for example — yield behaviors not found in natural materials that can be the basis for new devices, such as faster magnetic memory. “This is an exciting time for materials research at MIT. I am thrilled by the opportunities that MRL will bring to our community,” Beach says. “By providing a coordinated infrastructure to support the basic research, education, outreach, and industry activities of CMSE and MPC, the new MRL will be far more than the sum of its parts. CMSE has proven its ability to nucleate diverse research teams to pioneer new directions at the forefront of the field. I expect that MRL will further enhance the scope and impact of such coordinated efforts at MIT.”</p>
<p>The MIT Materials Research Laboratory kicks off with a seven-member Industry Collegium, made up of companies who wish to partner more closely with MIT researchers on innovative materials processing research and development projects. “By joining the MPC and CMSE, we’ll have a broader community, and we’ll also have a broader array of research topics with which to engage industry and form new partnerships,” Thompson says.&nbsp;</p>
The new MIT Materials Research Laboratory (MRL) will streamline the organization of materials research on campus and enhance collaboration, Vice President for Research Maria Zuber (center) says. To Zuber’s left is MRL Director Carl Thompson, the Stavros Salapatas Professor of Materials Science and Engineering. They are joined by newly named MRL Co-Director Geoffrey Beach, who is an associate professor of materials science and engineering. The center is housed in Building 13.Photo: Maria E. Aglietti/MRLMaterials Science and Engineering, Materials Research Laboratory, Research, Innovation and Entrepreneurship (I&E), DMSE, Energy, Photonics, Sustainability, Transportation, Physics, School of Engineering, School of Science, Materials Processing Center, Center for Materials Science and EngineeringStanislaw Olbert, professor emeritus of physics and a pioneering theorist of the space age, dies at 94http://news.mit.edu/2017/stanislaw-olbert-physics-professor-emeritus-and-pioneering-theorist-space-age-dies-1003
Olbert researched measurements of solar wind with instruments on several NASA space missions, including the Voyager probes. Tue, 03 Oct 2017 17:10:01 -0400Sandi Miller | Department of Physicshttp://news.mit.edu/2017/stanislaw-olbert-physics-professor-emeritus-and-pioneering-theorist-space-age-dies-1003<p><a href="http://web.mit.edu/physics/people/faculty/olbert_stanislaw.html" target="_blank">Stanislaw “Stan” Olbert</a> PhD ’53, professor emeritus of physics and a distinguished researcher with MIT’s <a href="http://web.mit.edu/space/www/" target="_blank">Space Plasma Group</a>, died from a heart attack on Sept. 23. He was 94.</p>
<p>Olbert fought with the Polish underground during World War II, came to MIT on a scholarship to earn his doctorate, and, as a member of MIT’s Space Plasma Group, was one of the pioneer theorists of the space age. He specialized in the understanding of the solar wind, the streams of atomic particles flowing outward from the sun. He participated in, and brought insight to, the measurements of the solar wind with instruments on several NASA space missions, including the <a href="https://en.wikipedia.org/wiki/Voyager_program" target="_blank">Voyager missions</a> to the outer planets and interstellar space.</p>
<p>Born in 1923, Olbert was raised by his widowed mother in a small village in Eastern Poland. He showed early academic promise, and, during the Russian occupation of 1939 to 1941, he concentrated in math and physics under Russian teachers. Under the subsequent German occupation of 1941, however, his studies were interrupted. He was forced to work as a mason, and later, because he spoke German, as a bookkeeper on a German-run farm. He secretly shared information about German-bound food shipments for later interception by the Polish underground.&nbsp;&nbsp;&nbsp;</p>
<p>In 1944, he fought in the Warsaw uprising and, at the surrender, was taken prisoner by the Germans. At the war’s end, Olbert was declared a "displaced person" and enrolled at the University of Munich to resume his studies in math and physics. He earned a scholarship to the doctoral program of MIT’s Department of Physics in 1949. With the Cosmic Ray Group led by Professor <a href="http://news.mit.edu/1993/rossi-1201" target="_self">Bruno Rossi</a>, he earned his doctorate in 1953, became an assistant professor in 1957, and became full professor in 1967; he retired in 1988.</p>
<p>Following his thesis research, Olbert studied the properties of high-energy nuclear interactions and the extensive air showers — large cascades of atomic particles propagating through the atmosphere — that are produced by those interactions. This provided the first theoretical framework in which the implications of various assumptions about the basic cascade processes could be worked out for comparison with observed shower phenomena.</p>
<p>Olbert’s research in the field of space plasmas began with a study of the origins of cosmic rays in our galaxy. This work, performed in collaboration with Rossi and Professor Philip Morrison, led Olbert into fundamental investigations of individual and collective behavior of charged particles in the interplanetary environment.</p>
<p>The results of these investigations became the basis of two MIT graduate courses. One of these, taught in collaboration with Rossi, led to the publication of a textbook on the subject, "<a href="https://www.amazon.com/Introduction-Physics-Space-Olbert-Rossi/dp/0070538298/ref=sr_1_1?s=books&amp;ie=UTF8&amp;qid=1506612965&amp;sr=1-1&amp;keywords=%22Introduction+to+the+Physics+of+Space%22">Introduction to the Physics of Space</a>" (McGraw-Hill, 1970).</p>
<p>“Professor Olbert was the theoretical backbone of MIT’s Space Plasma Group,” said his colleague <a href="http://web.mit.edu/physics/people/faculty/bradt_hale.html" target="_blank">Hale Bradt</a>, professor emeritus of physic<em>s</em>. The group flew instruments in numerous space missions to study the solar wind, beginning with its first in situ measurement with Explorer 10 in 1961, and including the 1977 launches of <a href="http://web.mit.edu/space/www/voyager_science.html" target="_blank">Voyager I and Voyager II</a>. Even today, the Voyagers continue to send data from in and beyond the heliosphere. Among other contributions, Olbert engaged in theoretical studies of a variety of mechanisms that could be responsible for the generation of stellar winds.</p>
<p>From 1979 to 1986, Olbert undertook two major research projects: the self-consistent solution of the problem of solar wind dynamics, and theoretical studies of radiation generated by solid conductors moving through a magnetized plasma. Olbert maintained contact with many graduate and undergraduate students who have since become well-known in the field of space research.</p>
<p>“He gave me private lessons on the physics of space plasmas, which had not been covered in my coursework,” said Olbert’s last doctoral student, Alan Barnett PhD ’83. “His cheerful and optimistic outlook was infectious.”</p>
<p>In the 1980s, Olbert was a frequent visitor to the University of Rome and the Arcetri Observatory in Florence; and, in 1991, at the Institute for Cosmic Studies in Warsaw, Poland. He collaborated abroad and at home with former students and associates on various projects. One of these papers, in 2003, provides methods for the visualization of the motion of electromagnetic fields that have been used in the teaching of freshman physics both at MIT and around the world. His last first-author paper was published in 2012, at the age of 89. Until late in his life, Olbert kept up with current events with regular reading of newspapers in German, Italian, Polish, and English.</p>
<p>He and his family lived in Melrose, Massachusetts, and later in Cambridge, with summers spent on their New Hampshire farm. Olbert is survived by his wife, Norma (DeVivo), and their two children, Thomas of Cambridge, and Elizabeth of Farmington, Maine, where she is adjunct professor at the University of Maine.</p>
<p>In 1980, Elizabeth created the abstract painting "<a href="http://space.mit.edu/sites/default/files/media/Jupiter_painting_1980_0.pdf" target="_blank">Jupiter</a>," inspired by the Voyager spacecraft images; it hangs in the headquarters of MIT’s Kavli Institute for Astrophysics and Space Research. In 2014, Norma published a biography of Olbert’s early years in Poland and Germany, "<a href="https://www.amazon.com/Boy-Lw%C3%B3w-Norma-Olbert/dp/1500455695">The Boy from Lwów</a>" (CreateSpace, 2014), for which Thomas wrote the foreword and Elizabeth designed the cover.</p>
<p>Olbert’s body was cremated, and there will be no funeral service. A memorial gathering will be announced in the near future.</p>
Stanislaw OlbertPhoto: Department of PhysicsFaculty, Obituaries, Physics, Space, astronomy and planetary science, NASA, School of ScienceMIT physicist Rainer Weiss shares Nobel Prize in physicshttp://news.mit.edu/2017/mit-physicist-rainer-weiss-shares-nobel-prize-physics-1003
LIGO inventor and professor emeritus of physics recognized “for decisive contributions to the LIGO detector and the observation of gravitational waves.”Tue, 03 Oct 2017 06:12:32 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/mit-physicist-rainer-weiss-shares-nobel-prize-physics-1003<p>Rainer Weiss ’55, PhD ’62, professor emeritus of physics at MIT, has won the Nobel Prize in physics for 2017. Weiss won half of the prize, with the other half of the award shared by Kip S. Thorne, professor emeritus of theoretical physics at Caltech, and Barry C. Barish, professor emeritus of physics at Caltech.</p>
<p>The Nobel Foundation, in its announcement this morning, cited the physicists <em>"</em>for decisive contributions to the LIGO detector and the observation of gravitational waves.”</p>
<p>“We are immensely proud of Rai Weiss, and we also offer admiring best wishes to his chief collaborators and the entire LIGO team,” says MIT President L. Rafael Reif. “The creativity and rigor of the LIGO experiment constitute a scientific triumph; we are profoundly inspired by the decades of ingenuity, optimism, and perseverance that made it possible. It is especially sweet that Rai Weiss not only served on the MIT faculty for 37 years, but is also an MIT graduate. Today’s announcement reminds us, on a grand scale, of the value and power of fundamental scientific research and why it deserves society’s collective support.”</p>
<p>At a press conference held today at MIT, Weiss credited his hundreds of colleagues who have helped to push forward the search for gravitational waves.</p>
<p>“The discovery has been the work of a large number of people, many of whom played crucial roles,” Weiss said. “I view receiving this [award] as sort of a symbol of the various other people who have worked on this.”</p>
<p>In describing what the award means to him in a larger context, Weiss said: “This prize and others that are given to scientists is an affirmation by our society of [the importance of] gaining information about the world around us from reasoned understanding of evidence."</p>
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<p><strong>Listening for a wobble</strong></p>
<p>On Sept. 14, 2015, at approximately 5:51 a.m. EDT, a gravitational wave — a ripple from a distant part of the universe — passed through the Earth, generating an almost imperceptible, fleeting wobble in the world that would have gone completely unnoticed save for two massive, identical instruments, designed to listen for such cosmic distortions.</p>
<p>The Laser Interferometer Gravitational-wave Observatory, or LIGO, consists of two L-shaped interferometers, each 4 kilometers in length, separated by 1,865 miles. On Sept. 14, 2015, scientists picked up a very faint wobble in the instruments and soon confirmed that the interferometers had been infinitesimally stretched — by just one-ten-thousandth the diameter of a proton — and that this minuscule distortion arose from a passing gravitational wave.</p>
<p>The LIGO Scientific Collaboration, with the Caltech-MIT LIGO Laboratory and more than 1,000 scientists at universities and observatories around the world, confirmed the signal as the first direct detection of a gravitational wave by an instrument on Earth. The scientists further decoded the signal to determine that the gravitational wave was the product of a violent collision between two massive black holes 1.3 billion years ago.</p>
<p>The momentous result confirmed the theory of general relativity proposed by Albert Einstein, who almost exactly 100 years earlier had predicted the existence of gravitational waves but assumed that they would be virtually impossible to detect from Earth. Since this first discovery, LIGO has detected three other gravitational wave signals, also generated by pairs of spiraling, colliding black holes; the most announced of a detection came <a href="http://news.mit.edu/2017/gravitational-waves-binary-black-hole-merger-observed-ligo-and-virgo-0927">just last week</a>.</p>
<p>“We are incredibly proud of Rai and his colleagues for their vision and courage that led to this great achievement,” says Michael Sipser, the Donner Professor of Mathematics and dean of the School of Science at MIT.&nbsp;“It is a wonderful day for them, for MIT, for risk-taking and boldness, and for all of science.”</p>
<p><strong>A gravitational blueprint</strong></p>
<p>The detection was an especially long-awaited payoff for Weiss, who came up with the initial design for LIGO some 50 years ago. He has since been instrumental in shaping and championing the idea as it developed from a desktop prototype to LIGO’s final, observatory-scale form.</p>
<p>In 1967, Weiss, then an assistant professor of physics at MIT, was asked by his department to teach an introductory course in general relativity — a subject he knew little about. A few years earlier, the American physicist Joseph Weber had claimed to have made the first detection of gravitational waves, using resonant bars — long, aluminum cylinders that should ring at a certain frequency in response to a gravitational wave. When his students asked him to explain how these Weber bars worked, Weiss found that he couldn’t.</p>
<p>No one in the scientific community had been able to replicate Weber’s results. Weiss had a very different idea for how to do it, and assigned the problem to his students, instructing them to design the simplest experiment they could to detect a gravitational wave. Weiss himself came up with a design: Build an L-shaped interferometer and shine a light down the length of each arm, at the end of which hangs a free-floating mirror. The lasers should bounce off the mirrors and head back along each arm, arriving where they started at the exact same time. If a gravitational wave passes through, it should “stretch” or displace the mirrors ever so slightly, and thus change the lasers’ arrival times.</p>
<p>Weiss refined the idea over a summer in MIT’s historic Building 20, a wooden structure built during World War II to develop radar technology. The building, meant to be temporary and known to many as the “Plywood Palace,” lived on to germinate and support innovative, high-risk projects. During that time, Weiss came to the conclusion that his design could indeed detect gravitational waves, if built to large enough dimensions. His design would serve as the essential blueprint for LIGO.</p>
<p><strong>An observatory takes shape</strong></p>
<p>To test his idea, Weiss initially built a 1.5-meter prototype. But to truly detect a gravitational wave, the instrument would have to be several thousand times longer: The longer the interferometer’s arms, the more sensitive its optics are to minute displacements.</p>
<p>To realize this audacious design, Weiss teamed up in 1976 with noted physicist Kip Thorne, who, based in part on conversations with Weiss, soon started a gravitational wave experiment group at Caltech. The two formed a collaboration between MIT and Caltech, and in 1979, the late Scottish physicist Ronald Drever, then of Glasgow University, joined the effort at Caltech. The three scientists — who became the co-founders of LIGO — worked to refine the dimensions and scientific requirements for an instrument sensitive enough to detect a gravitational wave.</p>
<p>Barry Barish soon joined the team as first a principal investigator, then director of the project, and was instrumental in securing funding for the audacious project, and bringing the detectors to completion.</p>
<p>After years of fits and starts in research and funding, the project finally received significant and enthusiastic backing from the National Science Foundation, and in the mid-1990s, LIGO broke ground, erecting its first interferometer in Hanford, Washington, and its second in Livingston, Louisiana.</p>
<p>Prior to making their seminal detection two years ago, LIGO’s detectors required years of fine-tuning to improve their sensitivity. During this time, Weiss not only advised on scientific quandaries but also stepped in to root out problems in the detectors themselves. Weiss is among the few to have walked the length of the interferometers’ tunnels in the space between LIGO’s laser beam tube and its encasement. Inspecting the detectors in this way, Weiss would often discover minute cracks, tiny shards of glass, and even infestations of wasps, mice, and black widow spiders, which he would promptly deal with.</p>
<p><strong>A cosmic path</strong></p>
<p>Weiss was born in 1932 in tumultuous Berlin. When his mother, Gertrude Loesner, was pregnant with Weiss, his father, neurologist Frederick Weiss, was abducted by the Nazis for testifying against a Nazi doctor. He was eventually released with the help of Loesner’s family. The young family fled to Prague and then emigrated to New York City, where Weiss grew up on Manhattan’s Upper West Side, cultivating a love for classical music and electronics, and making a hobby of repairing radios.</p>
<p>After graduating high school, he went to MIT to study electrical engineering, in hopes of finding a way to quiet the hiss heard in shellac records. He later switched to physics, but then dropped out of school in his junior year, only to return shortly after, taking a job as a technician in Building 20. There, Weiss met physicist Jerrold Zacharias, who is credited with developing the first atomic clock. Zacharias encouraged and supported Weiss in finishing his undergraduate degree in 1955 and his PhD in 1962.</p>
<p>Weiss spent some time at Princeton University as a postdoc, where he developed experiments to test gravity, before returning to MIT as an assistant professor in 1964. In the midst of his work in gravitational wave detection, Weiss also investigated and became a leading researcher in cosmic microwave background radiation — thermal radiation, found in the microwave band of the radio spectrum, that is thought to be a diffuse afterglow from the Big Bang.</p>
<p>In 1976, Weiss was appointed to oversee a scientific working group for NASA’s Cosmic Background Explorer (COBE) satellite, which launched in 1989 and went on to precisely measure microwave radiation and its tiny, quantum fluctuations. Weiss was co-founder and chair of the science working group for the mission, whose measurements helped support the Big Bang theory of the universe. COBE’s findings earned two of its principal investigators the Nobel Prize in physics in 2006.</p>
<p>Weiss has received numerous awards and honors, including the Medaille de l’ADION, the 2006 Gruber Prize in Cosmology, and the 2007 Einstein Prize of the American Physical Society. He is a fellow of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, and the American Physical Society, as well as a member of the National Academy of Sciences. In 2016, Weiss received a Special Breakthrough Prize in Fundamental Physics, the Gruber Prize in Cosmology, the Shaw Prize in Astronomy, and the Kavli Prize in Astrophysics, all shared with Drever and Thorne. Most recently, Weiss shared the Princess of Asturias Award for Technical and Scientific Research with Thorne, Barry Barish of Caltech, and the LIGO Scientific Collaboration.</p>
Rainer Weiss at home early this morning, after learning that he has won the 2017 Nobel Prize in physics.Photo: M. Scott BrauerAstrophysics, awards, Awards, honors and fellowships, LIGO, Black holes, Faculty, History, History of science, History of MIT, Kavli Institute, National Science Foundation (NSF), Nobel Prizes, Physics, Research, School of Science, Space, astronomy and planetary scienceShirley Jackson speaks about her career and being an agent for changehttp://news.mit.edu/2017/shirley-jackson-speaks-about-her-career-and-being-change-agent-0929
Professor Paula Hammond talks with MIT Corporation life member about her experiences as an MIT student, research scientist, and university president. Fri, 29 Sep 2017 16:35:01 -0400Julia C. Keller | School of Sciencehttp://news.mit.edu/2017/shirley-jackson-speaks-about-her-career-and-being-change-agent-0929<p>On Sept. 26, Shirley Ann Jackson&nbsp;’68 PhD ’73 returned to campus for a discussion with an audience of students, alumni, and friends about her career highlights and the direction of science education.</p>
<p>Jackson is the president of Rensselaer Polytechnic Institute (RPI) and an MIT Corporation life member. She received her bachelor’s degree from MIT in 1968, continuing her graduate work, in part, to create opportunities for other underrepresented minorities at MIT. She earned a doctorate in particle physics in 1973, becoming the first African American woman to receive a PhD from MIT and the second African American woman in the United States to earn a doctorate in physics.</p>
<p>Roughly 100 people, including students, alumni, and administrators joined Jackson for the conversation in the Media Lab, while others joined the <a href="https://www.facebook.com/groups/aewsaj/permalink/1830752983903849/">live Facebook webcast</a>. Paula Hammond, a David H. Koch Professor in Engineering and the head of MIT’s Department of Chemical Engineering, facilitated the conversation hosted by MIT School of Science, MIT School of Engineering, and the <a href="https://www.nationalmedals.org/stories/aewsaj" target="_blank">National Science and Technology Medals Foundation</a> (NSTMF).&nbsp;</p>
<p>Andy Rathmann-Noonan, executive director of NSTMF, opened the event by acknowledging Jackson as one of MIT’s 63 laureates who have received the nation’s highest honor in science or technology and innovation.</p>
<p>“Behind each one of these discoveries, and hundreds more, are extraordinary individuals who have struggled and persevered to answer some of the world’s biggest questions and solve its toughest challenges,” said Rathmann-Noonan. “But they were all in your shoes at one point in their lives.”</p>
<p>MIT President L. Rafael Reif then took the podium to introduce the evening’s distinguished alumna.</p>
<p>He spoke about Jackson’s time at MIT, including the “profoundly important role” that she played in the Task Force for Educational Opportunity, a group led by the <a href="http://news.mit.edu/2017/former-mit-president-paul-gray-dies-0918" target="_self">late Paul Gray</a>, MIT president during Jackson’s time as a student.</p>
<p>Reif said Jackson, Gray, and others on the taskforce “put MIT on the path to become the diverse community we know today. I believe, however, that it’s still worth asking that same question [posed by the taskforce]: ‘How can we together make this place change?’”</p>
<p><strong>Bees, <em>Brown v. Board of Ed,</em> and Sputnik</strong></p>
<p>Hammond began her line of questioning asking who or what inspired Jackson to pursue science. “Bumblebees got me started,” said Jackson who detailed how she would systematically observe and modify their behavior as a budding scientist interested in the natural world.</p>
<p>She also spoke about her parents as “aspirational role models,” specifically her father, an officer who earned a Bronze Star during World War II for an ingenious mechanical solution for amphibious vehicles with malfunctioning rudders.</p>
<p>Jackson said that the confluence of two events in her early education “changed her educational trajectory” toward science and engineering: the <em>Brown v. Board of Education</em> Supreme Court decision and the launch of Sputnik, the first satellite to orbit Earth launched by the Soviet Union.</p>
<p>With the <em>Brown v. Board of Education</em> Supreme Court case decision to desegregate public schools, in practical terms, Jackson said it mean that “instead of traveling miles across town, my sisters and I got to go to school around the corner,” said Jackson. The integration of the schools came with a new tracking system, and Jackson was placed in an accelerated honors track.&nbsp;</p>
<p>“That coincided with the interest in the country after the Sputnik launch to strengthen math and science in the public schools — and I am a public school product — and so I ended up with a very strong academic background,” Jackson said. “I was my high school valedictorian, and I came to MIT.”</p>
<p><strong>Change agent</strong></p>
<p>Hammond followed with the question: “At the time you decided to attend MIT there were very few people of color visible in the sciences anywhere, including on this campus. What was it like to be a black student entering MIT at that time?”&nbsp;</p>
<p>“On the one hand, it was exhilarating being at MIT.” Jackson replied. “I wanted to be a scientist and I loved the subject matter. But on the other, it was isolating and rather lonely. I can’t say it was easy. The academics were never the problem.”</p>
<p>Although admitting to being “a bit a nerd,” Jackson said that most of her “social life” happened off-campus, such as her membership in the Delta Sigma Theta sorority, which included friends in the audience such as Jennifer Rudd ’68 and Linda Sharpe ‘69, former president of the MIT Alumni Association.&nbsp;</p>
<p>In response to Hammond’s question about being a “change agent” to improve the quality of education for underrepresented minorities at MIT, Jackson detailed how she, Rudd, and Sharpe were galvanized by the murder of Martin Luther King Jr. in April of 1968.</p>
<p>“I had been a pretty quiet student before then, focusing on what I was doing: physics, working in the lab,” Jackson said. But after that pivotal event, Jackson gathered Rudd, Sharpe and others to “present some demands. By the time they were written, they were called ‘proposals.’”</p>
<p>The proposals that Jackson and others presented to then MIT President Gray formed the foundation of the Task Force for Educational Opportunity. Jackson described the discussions on financial aid, recruitment, and summer programming, which later became <a href="http://ome.mit.edu/programs-services/interphase-edge-empowering-discovery-gateway-excellence" target="_blank">MIT’s Interphase program</a> to boost the numbers of African-American students.</p>
<p>“We did go from having three to five African-American students per year, to 57 the year after we started the task force,” said Jackson. Hammond noted that Jackson was doing this work while a doctoral student in particle physics.</p>
<p>Jackson said completing the academic work was a foregone conclusion. “It’s important to focus on what one is here for. […] I felt that it was important that African-Americans, as I feel it’s important for many [others] to study and become scientists and engineers, and that I become one,” she said in a list of advice that she gave to students.</p>
<p><strong>Vision and leadership</strong></p>
<p>Hammond then switched gears to ask Jackson about her time at Bell Labs, as well as her time as the chair of the U.S. Nuclear Regulatory Commission (NRC) under President Bill Clinton.&nbsp;</p>
<p>“That was a big change because I had to walk away from my tenured professorship and what I was doing,” said Jackson who joined the NRC in 1995. Jackson talked about how nuclear incidents, such as the accident at Three-Mile Island and the Chernobyl disaster, were informing the nuclear industry and people’s perceptions about the future of nuclear power.</p>
<p>She said that she wanted to provide the NRC with a vision and direction to “reaffirm its fundamental health and safety mission and enhance its effectiveness” as a regulatory body. As chair, she also developed a new licensing and renewal process, as well as established the International Nuclear Regulators Association that still exists today.</p>
<p>In 1999, President Clinton asked Jackson to serve an additional term as NRC chair, but she opted instead to become president of RPI.</p>
<p>Hammond asked, “What was exciting and appealed to you about taking on this new role?”</p>
<p>“First of all, I’m an MIT grad, right?” Jackson said. “So to be able to become the president of another great technological university was a big thing.”</p>
<p>Hammond followed up by asking about Jackson’s thought process in laying out and executing a vision for RPI.</p>
<p>“[RPI] is a place that has turned out people who’ve made some of the greatest impacts, as MIT has, on our lives — not just nationally, but globally,” said Jackson. “The university needed an aspirational vision,” said Jackson, “and that was to become a top-tier, world-class technical research university with global reach and global impact.”</p>
<p>Hammond concluded the formal part of her questions by asking Jackson why, in an already busy schedule, she adds leadership positions such as serving on the President’s Council of Advisors on Science and Technology, the Secretary of Energy’s advisory board, and, most recently as co-chair of President Obama’s Intelligence Advisory Board.</p>
<p>“[There’s] a unique role that scientists and engineers can play in making a difference in people’s lives,” said Jackson. “Because of that, if I could do it, at the levels that I’ve been asked to do it, that it’s important to serve.”</p>
<p>Hammond then opened the floor to questions, many of which came from students, including one question from junior Anthony Rollins, current events co-chair of MIT’s Black Students Union.</p>
<p>“What made you want to leave tech and industry for administration and policy?” Rollins asked.&nbsp;</p>
<p>“There are many ways to make contributions. And one can make them directly being in science and engineering, but one may come a point where one feels there are ways to take that knowledge and background and have a broader impact across a broader front,” said Jackson. “But, I’ve never done public policy that doesn’t link to science and technology.”</p>
<p>“What I do today is less about my doing research directly, which is what I did early in my career, but enabling others and bringing along the next generation of scientists and engineers.”&nbsp;</p>
Shirley Jackson (right) answers a question from the audience at an event recounting her experiences as an MIT student and as a leader in nuclear science and higher education. MIT Professor Paula Hammond (left), head of the Department of Chemical Engineering, led the discussion. Photo: Johnny BuiSpecial events and guest speakers, Alumni/ae, Faculty, Physics, Diversity and inclusion, Nuclear science and engineering, Chemical engineering, MIT Corporation, School of Science, School of EngineeringFirst open-access data from large collider confirm subatomic particle patternshttp://news.mit.edu/2017/first-open-access-data-large-collider-subatomic-particle-patterns-0929
CERN Open Data Portal results reveal predictable patterns from colliding high-energy protons. Fri, 29 Sep 2017 09:37:15 -0400Jennifer Chu | MIT News Officehttp://news.mit.edu/2017/first-open-access-data-large-collider-subatomic-particle-patterns-0929<p>In November of 2014, in a first, unexpected move for the field of particle physics, the Compact Muon Solenoid (CMS) experiment — one of the main detectors in the world’s largest particle accelerator, the Large Hadron Collider — released to the public an immense amount of data, through a website called the CERN Open Data Portal.</p>
<p>The data, recorded and processed throughout the year 2010, amounted to about 29 terabytes of information, yielded from 300 million individual collisions of high-energy protons within the CMS detector. The sharing of these data marked the first time any major particle collider experiment had released such an information cache to the general public.</p>
<p>A new study by Jesse Thaler, an associate professor of physics at MIT and a long-time advocate for open access in particle physics, and his colleagues now demonstrates the scientific value of this move. In a paper published in <em>Physical Review Letters</em>, the researchers used the CMS data to reveal, for the first time, a universal feature within jets of subatomic particles, which are produced when high-energy protons collide. Their effort represents the first independent, published analysis of the CMS open data.</p>
<p>“In our field of particle physics, there isn’t the tradition of making data public,” says Thaler, who is a researcher in MIT's Laboratory for Nuclear Science. “To actually get data publicly with no other restrictions — that’s unprecedented.”</p>
<p>Part of the reason groups at the Large Hadron Collider and other particle accelerators have kept proprietary hold over their data is the concern that such data could be misinterpreted by people who may not have a complete understanding of the physical detectors and how their various complex properties may influence the data produced.</p>
<p>“The worry was, if you made the data public, then you would have people claiming evidence for new physics when actually it was just a glitch in how the detector was operating,” Thaler says. “I think it was believed that no one could come from the outside and do those corrections properly, and that some rogue analyst could claim existence of something that wasn’t really there.”</p>
<p>“This is a resource that we now have, which is new in our field,” Thaler adds. “I think there was a reluctance to try to dig into it, because it was hard. But our work here shows that we can understand in general how to use this open data, that it has scientific value, and that this can be a stepping stone to future analysis of more exotic possibilities.”</p>
<p>Thaler’s co-authors are Andrew Larkoski of Reed College, Simone Marzani of the State University of New York at Buffalo, and Aashish Tripathee and Wei Xue of MIT’s Center for Theoretical Physics and Laboratory for Nuclear Science.</p>
<p><strong>Seeing fractals in jets</strong></p>
<p>When the CMS collaboration publicly released its data in 2014, Thaler sought to apply new theoretical ideas to analyze the information. His goal was to use novel methods to study jets produced from the high-energy collision of protons.</p>
<p>Protons are essentially accumulations of even smaller subatomic particles called quarks and gluons, which are bound together by interactions known in physics parlance as the strong force. One feature of the strong force that has been known to physicists since the 1970s describes the way in which quarks and gluons repeatedly split and divide in the aftermath of a high-energy collision.</p>
<p>This feature can be used to predict the energy imparted to each particle as it cleaves from a mother quark or gluon. In particular, physicists can use an equation, known as an evolution equation or splitting function, to predict the pattern of particles that spray out from an initial collision, and therefore the overall structure of the jet produced.</p>
<p>“It’s this fractal-like process that describes how jets are formed,” Thaler says. “But when you look at a jet in reality, it’s really messy. How do you go from this messy, chaotic jet you’re seeing to the fundamental governing rule or equation that generated that jet? It’s a universal feature, and yet it has never directly been seen in the jet that’s measured.”</p>
<p><strong>Collider legacy</strong></p>
<p>In 2014, the CMS released a preprocessed form of the detector’s 2010 raw data that contained an exhaustive listing of “particle flow candidates,” or the types of subatomic particles that are most likely to have been released, given the energies measured in the detector after a collision.</p>
<p>The following year, Thaler published a theoretical paper with Larkoski and Marzani, proposing a strategy to more fully understand a complicated jet in a way that revealed the fundamental evolution equation governing its structure.</p>
<p>“This idea had not existed before,” Thaler says. “That you could distill the messiness of the jet into a pattern, and that pattern would match beautifully onto that equation — this is what we found when we applied this method to the CMS data.”</p>
<p>To apply his theoretical idea, Thaler examined 750,000 individual jets that were produced from proton collisions within the CMS open data. He looked to see whether the pattern of particles in those jets matched with what the evolution equation predicted, given the energies released from their respective collisions.&nbsp;</p>
<p>Taking each collision one by one, his team looked at the most prominent jet produced and used previously developed algorithms to trace back and disentangle the energies emitted as particles cleaved again and again. The primary analysis work was carried out by Tripathee, as part of his MIT bachelor's thesis, and by Xue.</p>
<p>“We wanted to see how this jet came from smaller pieces,” Thaler says. “The equation is telling you how energy is shared when things split, and we found when you look at a jet and measure how much energy is shared when they split, they’re the same thing.”</p>
<p>The team was able to reveal the splitting function, or evolution equation, by combining information from all 750,000 jets they studied, showing that the equation — a fundamental feature of the strong force — can indeed predict the overall structure of a jet and the energies of particles produced from the collision of two protons.</p>
<p>While this may not generally be a surprise to most physicists, the study represents the first time this equation has been seen so clearly in experimental data.&nbsp;</p>
<p>“No one doubts this equation, but we were able to expose it in a new way,” Thaler says. “This is a clean verification that things behave the way you’d expect. And it gives us confidence that we can use this kind of open data for future analyses.”</p>
<p>Thaler hopes his and others’ analysis of the CMS open data will spur other large particle physics experiments to release similar information, in part to preserve their legacies.</p>
<p>“Colliders are big endeavors,” Thaler says. “These are unique datasets, and we need to make sure there’s a mechanism to archive that information in order to potentially make discoveries down the line using old data, because our theoretical understanding changes over time. Public access is a stepping stone to making sure this data is available for future use.”</p>
<p>This research was supported, in part, by the MIT Charles E. Reed Faculty Initiatives Fund, the MIT Undergraduate Research Opportunities Program, the U.S. Department of Energy, and the National Science Foundation.</p>
The Compact Muon Solenoid is a general-purpose detector at the Large Hadron Collider.
Image courtesy of CERNData, Particles, Open access, Physics, Research, School of Science, National Science Foundation (NSF), Laboratory for Nuclear Science, Department of Energy (DoE)